Compression ignition internal combustion engine

ABSTRACT

It is an object of the present invention to provide a compression ignition internal combustion engine capable of making compatible an increase in compression self-ignition operating area with an optimum output torque control in the operating area and also smoothly switching between a self-ignition combustion and a spark ignition combustion. The compression ignition internal combustion engine operates by switching between the spark ignition combustion using an ignition device and the compression ignition combustion which self-ignites a mixture by piston compression. Variable valve mechanisms vary at least one of the valve timings and valve lifts of an intake valve and an exhaust valve. Intake air is regulated to vary the amount of air intake into a combustion chamber on the upstream side of a combustion chamber inlet of the compression ignition internal combustion engine. The variable valve mechanisms and the intake air regulation are controlled during the compression ignition combustion so as to perform the compression ignition combustion.

TECHNICAL FIELD

The present invention relates to a compression ignition internalcombustion engine, and more particularly, to a compression ignitioninternal combustion engine capable of switching a compression ignitioncombustion and a spark ignition combustion.

BACKGROUND ART

As described in JP-A-10-56413, a compression ignition internalcombustion engine adopts a combustion system of compressing andself-igniting a uniformly premixed fuel-air mixture. The compressionignition internal combustion engine can operate in an ultra-lean area(air-fuel ratio of 80 or more) that cannot be operated by a conventionalgasoline engine or diesel engine, and decreases flame temperatures andrealizes ignition combustion with a uniform fuel-air mixture, andtherefore it is an engine that allows drastic reduction of both NOx andsoot.

Generally, when a fuel-air premixture is compressed and reached at acertain temperature, a reaction called “low temperature oxidationreaction” whose initial reaction is dehydrogenation of hydrocarbon as afuel, starts. When this reaction progresses, an elementary reactioncalled “blue flame” takes place, which leads to self-ignition. Sincethis ignition takes place at multiple points in the fuel-air mixturesimultaneously, the combustion period for the combustion chamber as awhole is by far shorter than combustion by spark ignition of aconventional gasoline engine or a combustion period of injectioncombustion of a diesel engine. For this reason, this results in areduction of flame temperature and suppression of NOx generation whichis dependent on a duration thereof, which constitutes a factor ofrealizing low NOx in the compression ignition internal combustionengine.

However, the conventional compression ignition internal combustionengine has a problem that its output torque range is limited to a verynarrow range and an engine operation with compression ignition is onlyrealized within quite a limited range of low-load and low-speedrotation. The reason is that the temperature for a fuel-air premixtureusing hydrocarbon as a fuel to reach self-ignition is said to be 900K orhigher and a current gasoline engine whose compression ratio is set toabout 10 to 13 is known to have almost no operating area whereself-ignition can take place.

Furthermore, the compression ratio can be set as high as that of adiesel engine (16 to 22) and there can be an engine operating area byself-ignition of a fuel-air premixture, but since it is difficult forthe conventional engine to control self-ignition timings of the mixture,a combustion period is short and compression self-ignition of thepremixture is strongly affected by an air-fuel ratio, etc., its outputtorque range is limited to a very narrow range, causing a problem thatan engine operation by compression ignition can be realized only inquite a limited area of low-load and low-speed rotation.

In contrast, as described, for example, in JP-A-11-280507, an engine isknown which flows backward a high-temperature burnt gas (internal EGR)generated in a previous cycle to a combustion chamber by operating amechanism that makes variable valve timings of intake/exhaust valves,keeps the inside of the combustion chamber at a high temperature throughthe internal EGR in a low-load area and realizes an operating area bythe self-ignition combustion through control over the amount of theinternal EGR and real compression ratio and operates by the sparkignition combustion in a high-load area, area.

DISCLOSURE OF THE INVENTION

However, the internal combustion engine described in JP-A-11-280507: hasthe following problems. That is, the conventional internal combustionengine overlaps the opening periods of intake/exhaust valves tointroduce the internal EGR, which causes an amount of the internal EGRto be controlled by the overlapping period of the intake/exhaust valves.The conventional internal combustion engine also controls the intakevalve to control ignition timing at the same time. That is, when theopening/closing timings required for the intake valve and exhaust valvevary depending on the engine operating condition, both timings cannot becontrolled independently of each other, which causes a problem that theoperating area by self-ignition is narrowed.

Furthermore, the conventional engine system that combines theself-ignition combustion and the spark ignition combustion cannotcontrol valve timings and valve lifts of the intake/exhaust valves andthe amount of intake air independently of one another when switching acombustion state from the self-ignition combustion to the spark ignitioncombustion or from the spark ignition combustion to the self-ignitioncombustion, producing differences in torque causing a problem of makingstable driving of a vehicle difficult.

It is an object of the present invention to provide a compressionignition internal combustion engine capable of making compatible anincrease in compression self-ignition operating area with an optimumoutput torque control in the operating area and also smoothly switchingbetween a self-ignition combustion and a spark ignition combustion.

To attain the above object, the present invention provides a compressionignition internal combustion engine for operating by switching a sparkignition combustion using an ignition device and a compression ignitioncombustion for self-igniting a fuel-air mixture by piston compression,provided with variable valve mechanisms for varying at least one ofvalve timings and valve lifts of an intake valve and an exhaust valve,intake air regulating means for varying an amount of air intake into acombustion chamber on an upstream side of a combustion chamber inlet ofthe compression ignition internal combustion engine and control meansfor controlling the variable valve mechanisms and the intake airregulating means during a compression ignition combustion so as toperform a compression ignition combustion.

Such a configuration makes compatible an increase in the compressionself-ignition operating area with an optimum output torque control inthis operating area and also allows for smooth switching theself-ignition combustion and the spark ignition combustion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system block diagram showing a configuration of acompression ignition internal combustion engine according to a firstembodiment of the present invention;

FIG. 2 is a flow chart showing a method of deciding a combustion mode ofthe compression ignition internal combustion engine according to thefirst embodiment of the present invention;

FIG. 3 is a flow chart showing the contents of control of a first methodof controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIG. 4 is a schematic view of lifts of intake/exhaust valves in acompression ignition combustion mode of the compression ignitioninternal combustion engine according to the first embodiment of thepresent invention;

FIG. 5 is:another schematic view of lifts of intake/exhaust valves in acompression ignition combustion mode of the compression ignitioninternal combustion engine according to the first embodiment of thepresent invention;

FIG. 6 is a system block diagram showing a configuration forimplementing a third method of controlling the compression ignitioncombustion mode of the compression ignition internal combustion engineaccording to the first embodiment of the present invention;

FIG. 7 is a flow chart showing the contents of control of the thirdmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIGS. 8A and 8B illustrate the principle of detection of ignitiontimings for the compression ignition internal combustion engineaccording to the first embodiment of the present invention;

FIG. 9 is a flow chart showing the contents of control of a fourthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIG. 10 is a flow chart showing the contents of control of a fifthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIG. 11 is a flow chart showing the contents of control of a sixthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIG. 12 is a flow chart showing the contents of control of a seventhmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIG. 13 is a flow chart showing the contents of control of an eighthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIG. 14 is a flow chart showing the contents of control of a ninthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention;

FIG. 15 is a flow chart showing the contents of control in a compressionignition combustion mode in a low-speed, low-load state of a compressionignition internal combustion engine according to a second embodiment ofthe present invention;

FIG. 16 illustrates controlled variable of the variable valves in thecompression ignition combustion mode in a low-speed, low-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention;

FIG. 17 illustrates the state of the engine in the compression ignitioncombustion mode in a low-speed, low-load state of the compressionignition internal combustion engine according to the second embodimentof the present invention;

FIG. 18 is a flow chart showing the contents of control in thecompression ignition combustion mode in a high-speed, low-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention;

FIG. 19 illustrates controlled variables of the variable valves in thecompression ignition combustion mode in a high-speed, low-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention;

FIG. 20 illustrates the state of the engine in the compression ignitioncombustion mode in a high-speed, low-load state of the compressionignition internal combustion engine according to the second embodimentof the present invention;

FIG. 21 is a flow chart showing the contents of control in thecompression ignition combustion mode in a low-speed, high-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention;

FIG. 22 illustrates controlled variables of the variable valves in thecompression ignition combustion mode in a low-speed, high-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention;

FIG. 23 illustrates the state of the engine in the compression ignitioncombustion mode in a low-speed, high-load state of the compressionignition internal combustion engine according to the second embodimentof the present invention;

FIG. 24 is a flow chart showing the contents of control of switchingbetween a compression ignition combustion mode and spark ignitioncombustion mode of a compression ignition internal combustion engineaccording to a third embodiment of the present invention;

FIG. 25 illustrates control of switching between the compressionignition combustion mode and spark ignition combustion mode of thecompression ignition internal combustion engine according to the thirdembodiment of the present invention;

FIGS. 26A, 26B and 26C illustrate control of switching between thecompression ignition combustion mode and spark ignition combustion modeof the compression ignition internal combustion engine according to thethird embodiment of the present,invention;

FIG. 27 illustrates an air-fuel ratio in the compression ignitioncombustion mode and spark ignition combustion mode of the compressionignition internal combustion engine according to the third embodiment ofthe present invention;

FIG. 28 is a system block diagram showing a configuration of acompression ignition internal combustion engine according to a fourthembodiment of the present invention;

FIG. 29 is a system block diagram showing a configuration of acompression ignition internal combustion engine according to a fifthembodiment of the present invention;

FIG. 30 is a system block diagram showing a configuration of acompression ignition internal combustion engine according to a sixthembodiment of the present invention;

FIG. 31 is an operating area map for deciding a combustion method in acompression ignition internal combustion engine according to a seventhembodiment of the present invention;

FIG. 32 illustrates a heat generation curve;

FIG. 33 is a flow chart showing an operation of the compression ignitioninternal combustion engine according to the seventh embodiment of thepresent invention when compression ignition is prohibited;

FIG. 34 is an operating area map for deciding a combustion method in acompression ignition internal combustion engine according to an eighthembodiment of the present invention;

FIG. 35 is a flow chart showing an operation of the compression ignitioninternal combustion engine according to the eighth embodiment of thepresent invention when compression ignition is prohibited;

FIG. 36 is a flow chart showing an operation of a compression ignitioninternal combustion engine according to a ninth embodiment of thepresent invention when compression ignition is prohibited;

FIG. 37 is a system block diagram showing a, configuration of acompression ignition internal combustion engine according to a tenthembodiment of the present invention;

FIG. 38 is a flow chart showing a method of deciding a combustion modein the compression ignition internal combustion engine according to thetenth embodiment of the present invention; and

FIG. 39 is a flow chart showing a combustion mode switching controlmethod in the compression ignition internal combustion engine accordingto the tenth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to FIG. 1 to FIG. 14, a configuration and operationof a compression ignition internal combustion engine according to afirst embodiment of the present invention will be explained below.

First, a configuration of the compression ignition internal combustionengine according to the first embodiment will be explained by using FIG.1.

FIG. 1 is a system block diagram showing the configuration of thecompression ignition internal combustion engine according to the firstembodiment of the present invention.

The compression ignition internal combustion engine according to theembodiment can operate by switching between a spark ignition combustionusing an ignition device and a compression ignition combustionself-igniting a fuel-air mixture by piston compression.

A combustion chamber 16 is formed in a space enclosed by a cylinderblock 9, a piston 17 and a cylinder head 10. Reciprocating motion of thepiston 17 is transmitted to a crank shaft 21 through a connecting rod 20and converted to rotary motion. The combustion chamber 16 communicateswith an intake port 6 and an exhaust port 14. The path between theintake port 6 and the combustion chamber 16 is opened/closed by anintake valve 19 a. On the other hand, the path between the exhaust port14 and the combustion chamber 16 is opened/closed by an exhaust valve 19b. Valve lifts and the valve opening/closing timings of the intake valve19 a and the exhaust valve 19 b are controlled by variable valvemechanisms 15 a and 15 b respectively.

An ignition plug 13 is provided inside the combustion chamber 16. At thetime of the spark ignition combustion, spark discharge occurs from theignition plug 13 according to an instruction from an engine control unit1 (hereinafter referred to as “ECU”). At the time of a compressionignition combustion, the ignition plug 13 can also function as an ioncurrent detection device for detecting a combustion condition. The ECU 1monitors the combustion condition and ignition timings, etc. inside thecombustion chamber 16 according to detection signals of the ignitionplug 13.

Output values of an accelerator opening detection device 2 a and brakedepressing force detection device 2 b as driver intention detectingmeans for detecting the intention of a driver who operates a vehicleincorporating the compression ignition internal combustion engine areincorporated into the ECU 1 successively. Output values of a vehiclespeed detection device 2 c as vehicle driving condition detecting meansfor detecting a vehicle driving condition are incorporated into the ECU1 successively. Furthermore, output values from an air flow sensor 5, anintake manifold pressure sensor 8, an engine cooling water temperaturesensor 24, an air-fuel ratio sensor 22, a post-catalyst exhausttemperature sensor 23 provided after an catalyst 12 and a crank anglesensor 4 as engine operating state detecting means for detecting anengine operating condition are incorporated into the ECU 1 successively.Here, the air flow sensor 5 is preferably provided with the function ofmeasuring a intake air temperature and a value of the intake airtemperature detected by the air flow sensor 5 is also incorporated intothe ECU 1 simultaneously.

The ECU 1 calculates a load of the engine based on the output value ofthe accelerator opening detection device 2 a. That is, the acceleratoropening detection device 2 a also functions as engine load detectingmeans.

A fuel injection valve 11 is installed inside the intake port 6. In thisexample, the fuel injection valve 11 is assumed to be placed inside theintake port 6, but it is also possible to use a fuel injection valve ofa cylinder internal injection type that can directly inject fuel intothe combustion chamber 16.

A intake air regulating device 7 is provided inside the intake port 6. Athrottle valve is used as the intake air regulating device 7. As theintake air regulating device 7, it is preferable to use an electroniccontrol throttle valve, but it is also possible to use a mechanicalthrottle valve connected to an accelerator pedal via a wire.

The ECU 1 determines output torque of the engine based on an acceleratoropening signal detected by the accelerator opening detection device 2 aand a signal of an engine speed detected by the crank angle sensor 4 anddetermines the amount of fuel injection from the fuel injection valve 11and the amount of intake air adjusted by the intake air regulatingdevice 7. The ECU 1 controls the variable valve mechanisms 15 a and 15 bof the intake valve 19 a and the exhaust valve 19 b based on the decidedamount of intake air and also controls the intake air regulating device7. By the way, it is known that the compression ignition timing of theair-fuel mixture inside the combustion chamber 16 depends on atemperature history, pressure history inside the combustion chamber 16and air-fuel ratio of the mixture.

A characteristic configuration of the embodiment is that the compressionignition internal combustion engine is provided with the variable valvemechanisms 15 a and 15 b of the intake valve 19 a and the exhaust valve19 b and the intake air regulating device 7, and that the ECU 1 controlsthe variable valve mechanisms 15 a and 15 b and the intake airregulating device 7 according to the engine operating condition. Theconventional compression ignition internal combustion engine is designedto control only the variable valve mechanisms of the intake valve andexhaust valve and therefore its compression self-ignition operating areais narrow. On the other hand, the embodiment is designed to furthercontrol the amount of intake air and can thereby expand the compressionself-ignition operating area.

Then, a method of deciding the combustion mode of the compressionignition internal combustion engine according to the first embodimentwill be explained by using FIG. 2.

FIG. 2 is a flow chart showing a method of deciding a combustion mode ofthe compression ignition internal combustion engine according to thefirst embodiment of the present invention.

In step s100, the ECU 1 starts to select an operation mode (combustionmode).

First, in step s110, the ECU 1 takes in output values of the acceleratoropening detection device 2 a and the brake depressing force detectiondevice 2 b, which are the driver intention detecting means, and detectsthe intention of the driver who operates the vehicle incorporating thecompression ignition internal combustion engine.

Then, in step s120, the ECU 1 takes in a vehicle speed which is anoutput value of the vehicle speed detection device 2 c, which is thevehicle driving condition detecting means and an engine speed signaldetected by the crank angle sensor 4 to calculate a load of the engine.

Then, in step s130, the ECU 1 reads a cooling water temperature which isan output value of the engine cooling water temperature sensor 24.Furthermore, in step s140, the ECU 1 reads an exhaust temperature, whichis an output value of the post-catalyst exhaust temperature sensor 23.Furthermore, in step s150, the ECU 1 reads a intake air temperature bythe intake air temperature measuring function provided for the air flowsensor 5.

Then, in step s160, the ECU 1 decides a combustion method, whether acompression ignition combustion mode or a spark ignition combustionmode, based on the output values of the respective sensors and detectingmeans read in steps silo to s150. Conditions for operating by thecompression ignition combustion and conditions for operating by thespark ignition combustion are written in the ECU 1 beforehand todetermine a combustion method as respective maps for the acceleratoropening, air-fuel ratio, engine speed, intake air temperature, enginecooling water temperature and post-catalyst exhaust temperature sensors.Based on the prewritten maps and the outputs of the sensors, etc., theECU 1 determines the combustion method.

If the compression ignition combustion mode is selected in step s160,the process moves on to control in the compression ignition combustionmode in step s200. The details of the control in the compressionignition combustion mode will be explained later by using FIG. 3 andsubsequent figures. On the other hand, if the spark ignition combustionmode is selected in step s160, the process moves on to control in thespark ignition combustion mode in step s300.

An output torque of the internal combustion engine is determined by theamount of fuel injection and amount of intake air. Therefore, if theamount of fuel injection is written in the ECU 1 beforehand for theoutput torque of the engine decided according to the intention of thedriver, the vehicle driving condition, the engine operating conditionand the respective sensor output values, the amount of intake air iscontrolled. Furthermore, if the amount of intake air is writtenbeforehand in the ECU 1, the amount of fuel injection is controlled.

With reference to FIG. 3 to FIG. 8, a first to third control methods ofthe compression ignition combustion mode in the case where the amount offuel injection is written beforehand in the ECU 1 for the requiredoutput torque of the engine and the amount of intake air is controlledwill be explained. With reference to FIG. 9 and FIG. 10, a fourth andfifth control methods in the compression ignition combustion mode in thecase where the amount of intake air is written beforehand in the ECU 1for the required output torque of the engine and the amount of fuelinjection is controlled will be explained. Furthermore, with referenceto FIG. 11 and FIG. 12, a sixth and seventh control methods in thecompression ignition combustion mode in the case where the controlledvariables of the variable valve mechanisms 15 a and 15 b are writtenbeforehand in the ECU 1 for the required output torque of the engine andthe variable valve mechanisms 15 a and 15 b are controlled will beexplained. Furthermore, with reference to FIG. 13 and FIG. 14, an eighthand ninth control methods in the compression ignition combustion mode inthe case where the controlled variables of throttle valve opening arewritten beforehand in the ECU 1 for the required output torque of theengine and the throttle valve opening is controlled will be explained.

Next, a first method of controlling the compression ignition combustionmode of the compression ignition internal combustion engine according tothe embodiment will be explained by using FIG. 3.

FIG. 3 is a flow chart showing the content of control of the firstmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention.

In step s200, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode.

First, in step s210, the ECU 1 reads output values of the acceleratoropening detection device 2 a and the brake depressing force detectiondevice 2 b as the intention of the driver.

Then, in step s220, the ECU 1 takes in an output value of the vehiclespeed detection device 2 c as the vehicle driving condition and takes inoutput values of the accelerator opening detection device 2 a, theair-fuel ratio sensor 22, the crank angle sensor 4, the air flow sensor5 and intake air temperature sensor mounted on the air flow sensor 5,the engine cooling water temperature sensor 24 and the post-catalystexhaust temperature sensor 23 as the engine operating conditions.

Then, in step s230, the ECU 1 decides the output torque based on theoutput values read in step s210 and s220, searches for the fuelinjection amount map and target air-fuel ratio map stored in the ECU 1beforehand and selects the amount of fuel injection and the targetair-fuel ratio.

Then, in step s240, the ECU 1 decides a target amount of air based onthe target values of the amount of fuel injection and the targetair-fuel ratio selected in step s230.

Then, in step s250, the ECU 1 decides amounts of operation of thethrottle valve 7, the variable valve mechanisms 15 a and 15 b of theintake/exhaust valves according to the output value of the air flowsensor 5, the output value of the intake air temperature sensor in theair flow sensor 5 and the output value of the crank angle sensor 4.Since it is known that the compression ignition timing of the air-fuelmixture in the combustion chamber 16 depends on the temperature history,the pressure history and the air-fuel ratio of the mixture of thecombustion chamber 16, it is possible to determine the amounts ofoperation of the variable valve mechanisms 15 a and 15 b of the intakevalve and the exhaust valve and the intake air regulating device 7 withthese output values of the sensors. That is, the timing of closing theintake valve 19 a for realizing the optimum ignition timing is decidedaccording to the decided amount of intake air, the amount of internalEGR and the air-fuel ratio.

Then, in step s260, the ECU 1 operates the throttle valve 7 and thevariable valve mechanisms 15 a and 15 b of the intake/exhaust valvesbased on the amounts of operation decided in step s250.

Here, the first method of controlling the intake/exhaust valves in thecompression ignition combustion mode of the compression ignitioninternal combustion engine according to the embodiment will be explainedby using FIG. 4.

FIG. 4 is a schematic view of lifts of the intake/exhaust valves in thecompression ignition combustion mode of the compression ignitioninternal combustion engine according to the first embodiment of thepresent invention.

In FIG. 4, the horizontal axis shows a crank angle and the vertical axisshows valve lifts of the intake valve and the exhaust valve.

The lift level of the exhaust valve during the spark ignition combustionis as shown with solid line Ex1 in the drawing and suppose the maximumvalue of the level of the valve lift is L1. On the other hand, the liftlevel of the intake valve is as shown with single-dot dashed line Int1and suppose the maximum value of the level of the valve lift is L1.

On the other hand, the lift level of the exhaust valve 19 b during thecompression ignition combustion is as shown with dotted line Ex2 in thedrawing and suppose the maximum value of the level of the valve lift iscontrolled by the variable valve mechanism 15 b to L2, a value smallerthan that during the spark ignition combustion. On the other hand, as inthe case of the spark ignition combustion, the lift level of the intakevalve 19 a is as shown with single-dot dashed line. Int1 and the maximumvalue of the level of valve lift is L1.

That is, in the embodiment, a predetermined amount of exhaust gas istrapped by narrowing the area of the path between the exhaust port 14and the combustion chamber 16, that is, the area of the exhaust openingand an amount of heat necessary for self-ignition is secured by enthalpyof the exhaust gas. Here, the total thermal energy of the internal EGRis defined by both the amount of the internal EGR itself and the exhaustgas temperature which reaches a peak during a combustion at atheoretical air-fuel ratio (e.g., close to a air-fuel ratio of 14.7 inthe case of gasoline), and,therefore the valve lift level L is adjustedbased on the output value of the air flow sensor 5 and the output valueof the air-fuel ratio sensor 22 to secure the amount of heat necessaryfor the compression ignition.

When two or more exhaust valves 19 b are placed at the combustionchamber 16, the lift levels of the two valves are controlledindependently each other, which allows more accurate control of theamount of internal EGR. At this time, it is also possible to provide atemperature gradient in the combustion chamber 16 and control ignitiontimings by using a difference in the exhaust gas flow rate in thecommunication area between the exhaust port 14 and combustion chamber16, generating a flow in the combustion chamber 16 and controlling thecondition of a mixture of new air and the internal EGR gas.

Here, a second method of controlling the intake/exhaust valves in thecompression ignition combustion mode of the compression ignitioninternal combustion engine according to the embodiment will beexplained.

FIG. 5 is another schematic view of lifts of the intake/exhaust valvesin the compression ignition combustion mode of the compression ignitioninternal combustion engine according to the first embodiment of thepresent invention.

In addition to the method of reducing the level of valve lift of theexhaust valve as explained in FIG. 4, it is also possible to control thevariable valve mechanism 15 b so as to shorten the time of opening ofthe exhaust valve 19 b as another method of trapping the exhaust gas.

In FIG. 5, the horizontal axis shows a crank angle and the vertical axisshows valve lifts of the intake valve and the exhaust valve.

The lift level of the exhaust valve 19 b during a compression ignitioncombustion is as shown with dotted line Ex3 in the drawing and themaximum value of the level of valve lift is assumed to be lift level L1as in the case of a spark ignition combustion. However, the time ofopening of the exhaust valve 19 b is set to T3 by the variable valvemechanism 15 b. The opening time T3 of the exhaust valve 19 b iscontrolled to be a smaller value than the opening time T1 of the exhaustvalve during the spark ignition combustion shown in FIG. 4. The liftlevel of the intake valve 19 a is as shown with single-dot dashed lineInt1 as in the case of a spark ignition combustion and the maximum valueof the level of the valve lift is L1.

That is, in the embodiment, a predetermined amount of exhaust gas istrapped by narrowing the area of the path between the exhaust port 14and the combustion chamber 16, that is, the area of the exhaust openingand the amount of heat necessary for self-ignition is secured byenthalpy of the exhaust gas. Here, the total thermal energy of theinternal EGR is defined by both the amount of the internal EGR itselfand the exhaust gas temperature which reaches a peak during a combustionat a theoretical air-fuel ratio (e.g., close to an air-fuel ratio of14.7 in the case of gasoline), and therefore the opening time T3 of theexhaust valve is adjusted based on the output value of the air flowsensor 5 and the output value of the air-fuel ratio sensor 22 to securethe amount of heat necessary for the compression ignition.

Here, it is desirable to control the variable valve mechanism 15 b sothat the time of opening of the exhaust valve 19 b does not overlap withthe opening time of the intake valve 19 a. This is because when both theintake valve 19 a and the exhaust valve 19 b are open, the exhaust gasof the intake port 6 also flows back, making it difficult to control theamount of the internal EGR.

By the way, when two or more exhaust valves 19 b are placed at thecombustion chamber 16, the opening times of the two valves arecontrolled independently of each other, which allows more accuratecontrol of the amount of internal EGR. At this time, it is also possibleto provide a temperature gradient in the combustion chamber 16 andcontrol the ignition timing by using a difference in the exhaust gasflow rate in the communication area between the exhaust port 14 and thecombustion chamber 16, generating a flow in the combustion chamber 16and controlling the condition of a mixture of new air and the internalEGR gas.

Returning to FIG. 3, in step s270, the ECU 1 compares the output valueof the air flow sensor 5 with the amount of air decided by the targetair-fuel ratio and controls feedback of the throttle valve 7 and thevariable valve mechanisms 15 a and 15 b so as to have the same values.At this time, the closing timing of the intake valve 19 a has beendecided in step s250 and subsequent control of the amount of intake airis performed using valve lifts of the intake valve 19 a or the throttlevalve 7.

By the way, there is a plurality of combinations of the opening of thethrottle valve 7, the valve timings and the valve lifts of the intakevalve 19 a and the exhaust valve 19 b to realize the target amount ofair in step s240. In this case, it is desirable to perform control toattain a combination which will maximize the opening throttle valve 7 soas to realize a combination with the best fuel efficiency. This isbecause, when the opening of the throttle valve 7 is small, a negativepressure occurs inside the intake port 6 and the engine worksnegatively, that is, a so-called pumping loss is generated, whichreduces the fuel efficiency.

As explained above, the embodiment can secure the amount of internal EGRand determine appropriate ignition timings using the variable valvemechanisms 15 a and 15 b and further correct the amount of intake airusing the throttle valve 7, and can thereby perform an engine operationbest suited to the required torque. Thus, the embodiment can expand thecompression ignition combustion operating area.

Then, a third method of controlling the compression ignition combustionmode of the compression ignition internal combustion engine according tothe first embodiment of the present invention will be explained by usingFIG. 6 to FIG. 8.

First, the configuration of the compression ignition internal combustionengine according to the embodiment will be explained by using FIG. 6.

FIG. 6 is a system block diagram showing a configuration forimplementing the third method of controlling the compression ignitioncombustion mode of the compression ignition internal combustion engineaccording to the first embodiment of the present invention. By the way,in FIG. 6, the same reference numerals as those in FIG. 1 denote thesame parts.

In the embodiment, a pressure sensor 27 is placed in the combustionchamber 16 in addition to the configuration shown in FIG. 1. Thepressure sensor 27 is used to detect an initial pressure and ignitiontiming. The output values of the pressure sensor 27 are taken into theECU 1.

Then, the third method of controlling the compression ignitioncombustion mode of the compression ignition internal combustion engineaccording to the embodiment will be explained by using FIG. 7.

FIG. 7 is a flow chart showing the contents of control of the thirdmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention. By the way, the steps with the samereference numerals as those in FIG. 3 indicate the same contents ofcontrol.

In step s200A, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode with the third control content.

The contents of control in steps s210 to s260 are the same as thoseexplained in FIG. 3. In contrast to the procedure shown in step s270 inFIG. 3 where the output value of the air flow sensor 5 is compared withthe amount of air decided by the target air-fuel ratio and the throttlevalve 7 and the variable valve mechanisms 15 a and 15 b are subjected tofeedback control so that the two values match, the embodiment includesstep s265 and step s270A.

In step s265, the ECU 1 detects ignition timings from the output valueof the pressure sensor 27.

Here, a method of detecting ignition timings of the compression ignitioninternal combustion engine according to the embodiment will be explainedby using FIG. 8.

FIGS. 8A and 8B illustrate the principle of detection of ignitiontimings for the compression ignition internal combustion engineaccording to the first embodiment of the present invention.

In FIGS. 8A and 8B, the horizontal axis shows a crank angle, thevertical axis in FIG. 8A shows a heat generation rate and the verticalaxis in FIG. 8B shows a cylinder internal pressure.

The cylinder internal pressure waveform expressed with solid line inFIG. 8B is taken into the ECU 1 as the output value of the pressuresensor 27. The output value of the pressure sensor 27 is taken in withreference to the crank angle. The ECU 1 can predict ignition timingsbased on the output value of the pressure sensor 27. Furthermore, theECU 1 can correctly detect a compression ignition timing from a heatgeneration rate waveform (FIG. 8A) obtained by differentiating theoutput value of the pressure sensor 27. That is, FIG. 8A results fromdifferentiation of the waveform shown in FIG. 8B and the timing at whichthe heat generation rate rises at time t1 is the compression ignitiontiming.

Then, in step s270A of FIG. 7, the ECU 1 compares the target ignitiontiming with the actual ignition timing and further operates the throttlevalve 7 and the variable valve mechanisms 15 av and 15 b of theintake/exhaust valves so that the actual ignition timing coincides withthe target ignition timing. Here, the target ignition timing is presetin the ECU 1 as a value commensurate with the operating condition. Thetarget ignition timing is equal to the closing timing of the intakevalve 19 a.

In the above explanation, the ignition timing is detected by thepressure sensor, but it is also possible to detect an ion current usingthe both ends of the discharge section of the ignition plug 13 as theelectrodes and detect the ignition timing based on the output valuethereof.

As described above, the embodiment also allows the variable valvemechanisms 15 a and 15 b to secure the amount of internal EGR and set anappropriate ignition timing and further allows the throttle valve 7 tocorrect the amount of intake air, and can thereby perform an optimumengine operation with respect to the required torque. Therefore, theembodiment can expand the compression ignition combustion operatingarea.

Then, a fourth method of controlling the compression ignition combustionmode of the compression ignition internal combustion engine according tothe first embodiment of the present invention will be explained by usingFIG. 9.

FIG. 9 is a flow chart showing the contents of control of the fourthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention. By the way, the steps with the samereference numerals as those in FIG. 3 and FIG. 7 denote the samecontents of control.

In the embodiment, the amount of intake air with respect to the requiredoutput torque of the engine is written in the ECU 1 beforehand so as tocontrol the amount of fuel injection. The configuration of thecompression ignition internal combustion engine according to theembodiment is the same as that shown in FIG. 1.

In step s200B, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode with the fourth control content.

The contents of control in steps s210 and s220 are the same as thoseexplained in FIG. 3. Furthermore, the contents of control in steps s250and s260 are also the same as those explained in FIG. 3.

In step s230B, the ECU 1 searches for and decides a target amount of aircorresponding to the required output torque of the engine obtained insteps s210 and s220 using the target air amount map written in the ECU 1beforehand.

Then, in step s242, the ECU 1 takes in the output value of the air flowsensor 5 and detects the amount of intake air.

In steps s250 and s260, as in the case of FIG. 3, the ECU 1 decides theamount of operation of the throttle valve 7 and the variable valvemechanisms 15 a and 15 b of the intake/exhaust valves according to theoutput value of the intake air temperature sensor inside the air flowsensor 5 and the engine speed and operates the throttle valve 7 and thevariable valve mechanisms 15 a and 15 b.

Then, in step s263, the ECU 1 decides the amount of fuel injectionaccording to the output value of the air flow sensor 5 read in step s242and the target air-fuel ratio preset in the ECU 1 and allows the fuelinjection valve 11 to inject fuel.

Then, in step s270B, when the air-fuel mixture inside the combustionchamber 16 is burnt by a compression ignition and the burnt gas isexhausted out of the combustion chamber 16, the ECU 1 reads the air-fuelratio of the combustion gas exhausted into the exhaust port 14 using theair-fuel ratio sensor 22 and feeds back the amount of new fuel injectionand the amounts of operation of the throttle valve 7 and the variablevalve mechanisms 15 a and 15 b of the intake/exhaust valves from theoutput values, and thereby controls the engine operation. In this case,too, by reducing the level of valve lift of the exhaust valve 19 b andreducing the area of the exhaust opening, the ECU 1 can secure theamount of heat necessary for ignition through control of the amount ofinternal EGR.

As explained above, the embodiment can also secure the amount ofinternal EGR and determine appropriate ignition timing using thevariable valve mechanisms 15 a and 15 b and further correct the amountof intake air using the throttle valve 7, and can thereby perform anengine operation best suited to the required torque. Thus, theembodiment can expand the compression ignition combustion operatingarea.

Then, a fifth method of controlling the compression ignition combustionmode of the compression ignition internal combustion engine according tothe first embodiment of the present:invention will be explained by usingFIG. 10.

FIG. 10 is a flow chart showing the contents of control of the fifthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention. The steps with the same referencenumerals as those in FIG. 3, FIG. 7 and FIG. 9 show the same contents ofcontrol.

In the embodiment, the amount of intake air with respect to the requiredoutput torque of the engine is written in the ECU 1 beforehand tocontrol the amount of fuel injection. The configuration of thecompression ignition internal combustion engine according to theembodiment is the same as that shown in FIG. 6.

The embodiment adds control in steps s265C and s270C to the fourthcontrol method shown in FIG. 9. The contents of control in steps s265Cand s270C are equivalent to those in steps s265 and s270A in FIG. 7.

In step s200C, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode with the fifth control content.

The contents of control in steps s210 to s270B are the same as thoseexplained in FIG. 7.

In step s265C, the ECU 1 detects an ignition timing from the outputvalue of the pressure sensor 27. The method of detecting the ignitiontiming is the same as that explained in FIG. 8.

In step s270C, the ECU 1 compares the target ignition timing with theactual ignition timing and controls the throttle valve 7 and thevariable valve mechanisms 15 a and 15 b of the intake/exhaust valves sothat the actual ignition timing coincides with the target ignitiontiming. Here, the target ignition timing is preset in the ECU 1 as avalue commensurate with the operating condition. The ignition timingduring operation can also be detected by detecting an ion current usingthe both ends of the discharge section of the ignition plug 13 as theelectrodes and based on the output value thereof.

As described above, the embodiment also allows the variable valvemechanisms 15 a and 15 b to secure the amount of internal EGR and set anappropriate ignition timing and further allows the throttle valve 7 tocorrect the amount of intake air, and can thereby perform optimum engineoperation with respect to, the required torque. Therefore, theembodiment can expand the compression ignition combustion operatingarea.

Then, a sixth method of controlling the compression ignition combustionmode of the compression ignition internal combustion engine according tothe first embodiment of the present invention will be explained by usingFIG. 11.

FIG. 11 is a flow chart showing the contents of control of the sixthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention. By the way, the steps with the samereference numerals as those in FIG. 3. FIG. 7, FIG. 9 and FIG. 10 denotethe same contents of control.

In the embodiment, the controlled variables of the variable valvemechanisms 15 a and 15 b with respect to the required output torque ofthe engine are written in the ECU 1 beforehand so as to control thevariable valve mechanisms 15 a and 15 b. The configuration of thecompression ignition internal combustion engine according to theembodiment is the same as that shown in FIG. 6.

In step s200D, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode with the sixth control content.

The contents of control in steps s210 and s220 are the same as thoseexplained in FIG. 10.

In step s230D, the ECU 1 searches and decides the target variable valvecontrolled variables corresponding to the required output torque of theengine obtained in steps s210 and s220 using the target variable valvecontrolled variable map written in the ECU 1 beforehand.

Then, in step s261, the ECU 1 controls the variable valve mechanisms 15a and 15 b of the intake/exhaust valves based on the decision in steps230D. That is, in contrast to steps s250 and s260 in FIG. 10 where theECU 1 decides the amount of operation of the throttle valve 7 and thevariable valve mechanisms 15 a and 15 b of the intake/exhaust valves andoperates these throttle valve 7 and the variable valve mechanisms 15 aand 15 b, the embodiment controls both the throttle valve 7 and thevariable valve mechanisms 15 a and 15 b independently of each other.

Then, in step s263, the ECU 1 decides the amount of fuel injectionaccording to the required output torque of the engine and injects fuelusing the fuel injection valve 11.

Then, in step s270D, when the air-fuel mixture inside the combustionchamber 16 is burnt by compression ignition and the burnt gas isexhausted out of the combustion chamber 16, the ECU 1 reads the air-fuelratio of the combustion gas exhausted into the exhaust port 14 using theair-fuel ratio sensor 22 and feeds back the amount of new fuel injectionand the amount of operation of the throttle valve 7 from the outputvalues, and thereby controls the engine operation.

In step s265C, the ECU 1 detects the ignition timing based on the outputvalues of the pressure sensor 27. The method of detecting the ignitiontiming is the same as that explained in FIG. 8.

In step s270C, the ECU 1 compares the target ignition timing with theactual ignition timing and controls the throttle valve 7 and the amountof fuel injection so that the actual ignition timing coincides with thetarget ignition timing. Here, the target ignition timing is preset inthe ECU 1 as a value commensurate with the operating condition. Theignition timing during operation can also be detected by detecting anion current using the both ends of the discharge section of the ignitionplug 13 as the electrodes and based on the output value thereof.

As described above, the embodiment also allows the variable valvemechanisms 15 a and 15 b to secure the amount of internal EGR and setappropriate ignition timing and further allows the throttle valve 7 tocorrect the amount of intake air, and can thereby perform optimum engineoperation with respect to the required torque. Therefore, the embodimentcan expand the compression ignition combustion operating area.

Then, a seventh method of controlling the compression ignitioncombustion mode of the compression ignition internal combustion engineaccording to the first embodiment of the present invention will beexplained by using FIG. 12.

FIG. 12 is a flow chart showing the contents of control of the seventhmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention. By the way, the steps with the samereference numerals as those in FIG. 11 denote the same contents ofcontrol.

In the embodiment, the controlled variables of the variable valvemechanisms 15 a and 15 b with respect to the required output torque ofthe engine are written in the ECU 1 beforehand so as to control thevariable valve mechanisms 15 a and 15 b. The configuration of thecompression ignition internal combustion engine according to theembodiment is the same as that shown in FIG. 6.

The embodiment uses the contents of control in steps s270E1 and s270E2instead of steps s270D and s270C in FIG. 11.

In step s200E, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode with the seventh control content.

The contents of control in steps s210 to s267 are the same as thoseexplained in FIG. 11.

In step s270E1, when the air-fuel mixture inside the combustion chamber16 is burnt by the compression ignition and the burnt gas is exhaustedout of the combustion chamber 16, the ECU 1 reads the air-fuel ratio ofthe combustion gas exhausted into the exhaust port 14 using the air-fuelratio sensor 22 and feeds back the amount of new fuel injection and theamounts of operation of the variable valve mechanisms 15 a and 15 b andthe throttle valve 7 from the output values, and thereby controls theengine operation. At this time, the process is fed back to a point justbefore step s261. Therefore, the amounts of operation of the variablevalve mechanisms 15 a and 15 b in addition to the content of control inFIG. 11 are also fed back.

In step s265C, the ECU 1 detects an ignition timing from the outputvalue of the pressure sensor 27. The method of detecting the ignitiontiming is the same as that explained by using FIG. 8.

In step s270E2, the ECU 1 compares the target ignition timing with theactual ignition timing and controls the amounts of operation of thethrottle valve 7 and the variable valve mechanisms 15 a and 15 b and theamount of fuel injection so that the actual ignition timing coincideswith the target ignition timing. At this time, the process is fed backto a point just before step s261. Therefore, in addition to the contentof control in FIG. 11, the amounts of operation of the variable valvemechanisms 15 a and 15 b are also fed back.

As described above, the embodiment also allows the variable valvemechanisms 15 a and 15 b to secure the amount of internal EGR and setappropriate ignition timing and further allows the throttle valve 7 tocorrect the amount of intake air, and can thereby perform optimum engineoperation with respect to the required torque. Therefore, the embodimentcan expand the compression ignition combustion operating area.

According to the sixth or seventh control method described in FIG. 11 orFIG. 12, it is possible to write complicated calculations of controlledvariables of the variable valve mechanisms 15 a and 15 b in the ROMbeforehand and correct the amount of intake air by the throttle valve 7with respect to the target air-fuel ratio, and therefore it is possibleto perform optimum operation of the engine with respect to the requiredtorque and reduce calculation load of the ECU 1 while securing theperformance of the engine operation with low exhaust and low fuelconsumption.

Then, an eighth method of controlling the compression ignitioncombustion mode of the compression ignition internal combustion engineaccording to the first embodiment of the present invention will beexplained by using FIG. 13.

FIG. 13 is a flow chart showing the contents of control of the eighthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention. By the way, the steps with the samereference numerals as those in FIG. 3 to FIG. 12 denote the samecontents of control.

In the embodiment, the controlled variable of the throttle valve openingwith respect to the required output torque of the engine is written inthe ECU 1 beforehand to control the throttle valve opening. Theconfiguration of the compression ignition internal combustion engineaccording to the embodiment is the same as that shown in FIG. 1.

In step s200F, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode with the eighth control content.

The contents of control in steps s210 and s220 are the same as thoseexplained in FIG. 3.

In step s230F, the ECU 1 searches and decides the target throttle valveopening controlled variable corresponding to the required output torqueof the engine obtained in steps s210 and s220 using the target throttlevalve opening controlled variable map written in the ECU 1 beforehand.

Then, in step s262, the ECU 1 controls the opening of the throttle valve7 based on the controlled variable of throttle valve opening decided instep s230F.

In step s263, the ECU 1 decides the amount of fuel injectioncorresponding to the required output torque of the engine and injectsfuel by the fuel injection valve 11.

Then, in step s267, the ECU 1 decides the amounts of operation of thevariable valve mechanisms 15 a and 15 b according to the output value ofthe air flow sensor 5, the output value of the intake air temperaturesensor inside the air flow sensor 5 and the engine speed.

Then, in step s270F, when the air-fuel mixture inside the combustionchamber 16 is burnt by compression ignition and the burnt gas isexhausted out of the combustion chamber 16, the ECU 1 reads the air-fuelratio of the combustion gas exhausted into the exhaust port 14 using theair-fuel ratio sensor 22 and feeds back the amount of new fuel injectionand the amounts of operation of the variable valve mechanisms 15 a and15 b of the intake/exhaust valves from the output values, and therebycontrols the engine operation. In this case, too, by reducing the levelof valve lift of the exhaust valve 19 b and reducing the area of theexhaust opening, the ECU 1 can secure the amount of heat necessary forignition through control of the amount of internal EGR.

As explained above, the embodiment can also secure the amount ofinternal EGR and determine appropriate ignition timing using thevariable valve mechanisms 15 a and 15 b and further correct the amountof intake air using the throttle valve 7, and can thereby perform anengine operation best suited to the required torque. Thus, theembodiment can expand the compression ignition combustion operatingarea.

Then, a ninth method of controlling the compression ignition combustionmode of the compression ignition internal combustion engine according tothe first embodiment of the present invention will be explained by usingFIG. 14.

FIG. 14 is a flow chart showing the contents of control of the ninthmethod of controlling the compression ignition combustion mode of thecompression ignition internal combustion engine according to the firstembodiment of the present invention. The steps with the same referencenumerals as those in FIG. 3 to FIG. 13 show the same contents ofcontrol.

In the embodiment, the controlled variable of the throttle valve openingwith respect to the required output torque of the engine is written inthe ECU 1 beforehand to control the opening of the throttle valve. Theconfiguration of the compression ignition internal combustion engineaccording to the embodiment is the same as that shown in FIG. 6.

The embodiment adds control in steps s265G and s270G to the eighthcontrol method shown in FIG. 13. The contents of control in steps s265Gand s270G are equivalent to those in steps s265 and s270A in FIG. 7.

In step s200G, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode with the ninth control content.

The contents of control in steps s210 to s270F are the same as thoseexplained in FIG. 13.

In step s265G, the ECU 1 detects ignition timing from the output valueof the pressure sensor 27. The method of detecting ignition timing isthe same as that explained in FIG. 8.

In step s270G, the ECU 1 compares the target ignition timing with theactual ignition timing and controls the amount of fuel injection and thevariable valve mechanisms 15 a and 15 b of the intake/exhaust valves sothat the actual ignition timing coincides with the target ignitiontiming. Here, the target ignition timing is preset in the ECU 1 as avalue commensurate with the operating condition. The ignition timingduring operation can also be detected by detecting an ion current usingthe both ends of the discharge section of the ignition plug 13 as theelectrodes and the ignition timing based on the output value thereof.

As described above, the embodiment also allows the variable valvemechanisms 15 a and 15 b to secure the amount of internal EGR and setappropriate the ignition timing and further allows the throttle valve 7to correct the amount of intake air, and can thereby perform optimumengine operation operating area.

As described above, the control methods of the first embodiment of thepresent invention can control various parameters such as the setting ofignition timings, the amount of internal EGR (temperature inside thecombustion chamber 16) and the amount of intake air independentlythrough control of the throttle valve 7 and the variable valvemechanisms 15 a and 15 b of the intake valve 19 a and the exhaust valves19 b, and can thereby continue optimum engine operation with lowexhaust, low fuel consumption without producing torque leveldifferences.

Then, with reference now to FIG. 15 to FIG. 23, a configuration andoperation of a compression ignition internal combustion engine accordingto a second embodiment of the present invention will be explained below.

The configuration of the compression ignition internal combustion engineaccording to the embodiment is the same as that shown in FIG. 6. Theembodiment changes control over the throttle valve and the variablevalve mechanisms according to the operating condition of the engine inthe compression ignition combustion mode.

First, the method of controlling the compression ignition combustionmode of the compression ignition internal combustion engine according tothe embodiment in a low-speed, low-load state will be explained by usingFIG. 15 to FIG. 17.

FIG. 15 is a flow chart showing the contents of control in thecompression ignition combustion mode in a low-speed, low-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention. Furthermore, FIG. 16illustrates controlled variable of the variable valves in a compressionignition combustion mode in a low-speed, low-load state of thecompression ignition internal combustion engine according to the secondembodiment of the present invention and FIG. 17 illustrates a state ofthe engine in the compression ignition combustion mode in a low-speed,low-load state of the compression ignition internal combustion engineaccording to the second embodiment of the present invention. In FIG. 17,the same reference numerals as those in FIG. 6 denote the same parts.

In step s200H, the ECU 1 starts a variable valve mechanism, throttlevalve controlled variable decision routine in the compression ignitioncombustion mode in a low-speed, low-load state.

First, in step s210 the ECU 1 reads output values of the acceleratoropening detection device 2 a and brake depressing force detection device2 b as the intention of the driver.

Then, in step s220, the ECU 1 takes in an output value of the vehiclespeed detection device 2 c as the vehicle driving condition and takes inoutput values of the accelerator opening detection device 2 a, theair-fuel ratio sensor 22, the crank angle sensor 4, the air flow sensor5 and the intake air temperature sensor mounted on the air flow sensor5, the engine cooling water temperature sensor 24 and the post-catalystexhaust temperature sensor 23 as the engine e operating conditions. Theprocess moves on to step s230 when the engine operating conditions areset to a low-speed, low-load state, while the process moves on to steps261I in FIG. 18 when the engine operating conditions a re set to ahigh-speed, low-load state and the process moves on to step s261J inFIG. 21 when the engine operating conditions are set to a low-speed,high-load state.

In the case of a low-speed, low-load state, in step s230, the ECU 1decides the output torque based on the output values read in step s210and s220, searches for the fuel injection amount map and the targetair-fuel ratio map stored in the ECU 1 beforehand and selects the amountof fuel injection and the target air-fuel ratio.

Then, in step s240, the ECU 1 decides the target air amount based on theamount of fuel injection and target air-fuel ratio selected in steps230.

Then, in step s250, the ECU 1 decides amounts of operation of thethrottle valve 7 and the variable valve mechanisms 15 a And 15 b of theintake/exhaust valves according to the output value of the air flowsensor 5, the output value of the intake air temperature sensor in theair flow sensor 5 and the output value of the crank angle sensor 4.Since it is known that the compression ignition timing of the air-fuelmixture in the combustion chamber 16 depends on the temperature history,the pressure history and the air-fuel ratio of the air-fuel mixture ofthe combustion chamber 16, it is possible to determine the amounts ofoperation of the variable valve mechanisms 15 a and 15 b of the intakevalve and exhaust the valve and the intake air regulating device 7. Thatis, the closing timing of the intake valve 19 a for realizing an optimumignition timing is decided according to the decided intake air, theamount of internal EGR and air-fuel ratio.

Then, in step s260, the ECU 1 operates the throttle valve 7 and thevariable valve mechanisms 15 a and 15 b of the intake/exhaust valvesbased on the amounts of operation decided in step s250.

Here, the method of controlling the intake/exhaust valves in thecompression ignition combustion mode of the compression ignitioninternal combustion engine according to the embodiment will be explainedby using FIG. 16 and FIG. 17.

As shown in FIG. 17, the opening of the throttle valve 7 is set to berelatively small. This is because the filling efficiency needs to be setto a small value since the compression ignition internal combustionengine is in a low-load, low-speed area.

In FIG. 16, the horizontal axis shows a crank angle and the verticalaxis shows valve lifts of the intake valve and the exhaust valve.

The lift level of the exhaust valve during the spark ignition combustionis as shown with solid line Ex1 in the drawing and suppose the maximumvalue of the level of valve lift is L1. On the other hand, the liftlevel of the intake valve is as shown with single-dot dashed line Int1and suppose the maximum value of the level of valve lift is L1.

On the other hand, the lift level of the intake valve 19 a during thecompression ignition combustion under a low-speed, low-load operatingcondition is as shown with 2-dot dashed line Int2 in the drawing, theclosing timing of the intake valve 19 a (time t2) is relatively early,and the lift level of the intake valve 19 a is set to L3, a valuerelatively small. The level of valve lift of the exhaust valve 19 b isas shown with dotted line Ex2 in the drawing and suppose the maximumvalue of the level of the valve lift is controlled by the variable valvemechanism 15 b to L2, a value smaller than that during the sparkignition combustion. Making the level of valve lift of the exhaust valve19 b during the compression ignition combustion lower than that during aspark ignition combustion gives an effect of reducing the amount of theexhaust gas and controlling the internal EGR, while further reducing thelevel of valve lift of the exhaust valve 19 b in the case of alow-speed, low-load state decreases the filling efficiency of the intakeair and secures more internal EGR. When, for example, cam type variablevalve mechanisms are used, controlling the valve lifts to a small valuecan reduce friction loss due to a cam drive force phenomenon, andthereby reduce fuel consumption drastically and expand the compressionignition combustion operating area toward the high-load side.

Next, in step s270, the ECU 1 compares the output value of the air flowsensor 5 with the amount of air decided by the target air-fuel ratio andcontrols feedback of the throttle valve 7 and the variable valvemechanisms 15 a and 15 b so that the two values match. At this time, theclosing timing of the intake valve 19 a has been decided in step s250and subsequent control of the amount of intake air is performed usingvalve lifts of the intake valve 19 a or the throttle valve 7.

Then, in step s280, the ECU 1 decides whether an operating conditionthat satisfies the required torque exists or not by controlling thevariable valve mechanisms 15 a and 15 b and the amount of fuel injectioneven if the opening of the throttle valve 7 is relatively large in alow-load, low-speed area and if such an operating condition exists, theECU 1 selects a combination with the maximum opening of the throttlevalve 7, that is, the best fuel efficiency, while keeping the internalEGR rate constant inside the combustion chamber 16 of the engine.

Then, the method of controlling the compression ignition combustion modein a high-speed, low-load state of the compression ignition internalcombustion engine according to the embodiment will be explained by usingFIG. 18 to FIG. 20.

FIG. 18 is a flow chart showing the contents of control in thecompression ignition combustion mode in a high-speed, low-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention. Furthermore, FIG. 19illustrates controlled variables of the variable valves in thecompression ignition combustion mode in a high-speed, low-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention and FIG. 20 illustrates astate of the engine in the compression ignition combustion mode in ahigh-speed, low-load state of the compression ignition internalcombustion engine according to the second embodiment of the presentinvention. By the way, in FIG. 19, the same reference numerals as thosein FIG. 16 denote the same parts. In FIG. 20, the same referencenumerals as those in FIG. 6 denote the same parts.

In step s220 in FIG. 15, when the engine speed increases and ahigh-speed, low-load state is created under an engine operatingcondition, the process moves on to step s261I in FIG. 18.

When the engine speed increases, a one-cycle elapsed time is shortened,which in turn shortens the high-temperature residence time of theair-fuel mixture, and therefore realizing compression ignition requiresthe compression ratio to be increased to increase an ultimatetemperature inside the combustion chamber 16 or the internal temperatureof the combustion chamber 16 at the beginning of compression to be setto a high value. At the same time, kinetic energy of the intake airincreases, and therefore a pulsation flow inside the intake port 6changes and the valve closing timing of the intake valve 19 a at whichthe filling efficiency reaches a maximum shifts toward the phase lagside.

Thus, in step s261I, the ECU 1 manipulates the level of lift of theexhaust valve 19 b using the variable valve mechanism 15 b so that thearea of the exhaust opening increases as the engine speed increases.

That is, as shown in FIG. 19, the lift level of the exhaust valve 19 bduring a compression ignition combustion under a high-speed, low-loadoperating condition is as shown with dotted line Ex3 in the drawing andthe lift level of the exhaust valve 19 b is assumed to be L4, which isgreater than the lift level L2 of the exhaust valve 19 b under alow-speed, low-load operating condition.

Then, in step s267I, the ECU 1 increases the opening of the throttlevalve 7 to control the amount of intake air so that the air-fuel ratioof the mixture approaches a theoretical air-fuel ratio with respect toan amount of fuel injection preset under the engine operating condition.This is because bringing the air-fuel ratio of the mixture closer to thetheoretical air-fuel ratio increases the combustion gas temperature andincreases the amount of intake air, and thereby decreases the internalEGR rate, thus preventing an incidental decrease in the temperatureinside the combustion chamber 16 necessary for a compression ignitioncombustion at the beginning of compression.

Then, in step s262I, the ECU 1 controls the variable valve mechanism 15a on the intake side so as to select appropriate ignition timing. Duringa compression ignition combustion under a high-speed, low-load operatingcondition, the level of valve lift of the intake valve 19 a is as shownwith 2-dot dashed line Int3 in the drawing and the closing timing (timet3) of the intake valve 19 a is later than the closing timing (time t2)in a low-speed, low-load state and the level of valve lift of the intakevalve 19 a is set to L1, which is greater than the level of lift L3 in alow-speed, low-load state.

Then, in step s263I, the ECU 1 decides the amount of fuel injectionaccording to the amount of intake air controlled in step s267I and thetarget air-fuel ratio preset in the ECU 1 and injects fuel using thefuel injection valve 11.

Then, in step s270I, the ECU 1 reads the air-fuel ratio of thecombustion gas using the air-fuel ratio sensor 22 and feeds back theamount of new fuel injection and the amounts of operation of throttlevalve 7 and the variable valve mechanisms 15 a and 15 b of theintake/exhaust valves based on the output values thereof, and therebycontrols engine operation.

Then, in step s265I, the ECU 1 detects ignition timing based on theoutput value of the pressure sensor 27. Then, in step s270I2, the ECU 1compares the target ignition timing with the,actual ignition timing andcontrols the throttle valve 7 and the variable valve mechanisms 15 a and15 b of the intake/exhaust valves so that the actual ignition timingcoincides with the target ignition timing. Here, the target ignitiontiming is preset in the ECU 1 as a value commensurate with the operatingcondition.

At this time, to prevent vibration, etc. in the engine, it is necessaryto control the output value of the air flow sensor 5 to a constant valueso that the amount of intake air does not change discontinuously duringan operation of the variable valve mechanisms 15 a and 15 b. This isbecause the amount of intake air or air-fuel ratio changes drasticallydepending on time response of the variable valve mechanisms 15 a and 15b, causing the operator to have uncomfortable feeling or causedeterioration of exhaust due to accidental fire. That is, to keep normaloperation of the engine against variations in the engine speed, it isnecessary to perform concerted control between the throttle valve 7 andvariable valve mechanisms 15 a and 15 b as described above.

Then, the method of controlling the compression ignition combustion modeunder a low-speed, high-load operating condition of the compressionignition internal combustion engine according to the embodiment will beexplained by using FIG. 21 to FIG. 23.

FIG. 21 is a flow chart showing the contents of control in thecompression ignition combustion mode in a low-speed, high-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention. Furthermore, FIG. 22illustrates controlled variables of the variable valves in thecompression ignition combustion mode in a low-speed, high-load state ofthe compression ignition internal combustion engine according to thesecond embodiment of the present invention. FIG. 23 illustrates thestate of the engine in the compression ignition combustion mode in alow-speed, high-load state of the compression ignition internalcombustion engine according to the second embodiment of the presentinvention. By the way, in FIG. 22, the same reference numerals as thosein FIG. 16 denote the same parts. In FIG. 23, the same referencenumerals as those in FIG. 6 denote the same parts.

In step s220 in FIG. 15, when the engine load increases and ahigh-speed, low-load state is created under an engine operatingcondition, the process moves on to step s261J in FIG. 21. When the loadincreases, required torque also increases and therefore the efficiencyof filling the engine needs to be increased.

Thus, in step s261J, the ECU 1 manipulates lifts of the exhaust valve 19b using the variable valve mechanism 15 b so that the area of theexhaust opening increases as the load increases.

That is, as shown in FIG. 22, the level of valve lift of the exhaustvalve 19 b during a compression ignition combustion under a low-speed,high-load operating condition is as shown with dotted line Ex4 in thedrawing and the lift level of the exhaust valve 19 b is assumed to beL4, which is greater than the lift level L2 of the exhaust valve 19 bunder a low-speed, low-load operating condition.

Then, in step s267J, the ECU 1 increases the opening of the throttlevalve 7 to control the amount of intake air so that the air-fuel ratioof the mixture approaches a theoretical air-fuel ratio with respect toan amount of fuel injection preset under the engine operating condition.This is because bringing the air-fuel ratio of the mixture closer to thetheoretical air-fuel ratio increases the combustion gas temperature andincreases the amount of intake air, which decreases the internal EGRrate, thus preventing an incidental decrease in the temperature insidethe combustion chamber 16 necessary for a compression ignitioncombustion at the beginning of compression.

Then, in step s262J, the ECU 1 controls the variable valve mechanism 15a on the intake side so as to select appropriate ignition timing. Duringa compression ignition combustion under a low-speed, high-load operatingcondition, the level of valve lift of the intake valve 19 a is as shownwith 2-dot dashed line Int4 in the drawing and the closing timing (timet4) of the intake valve 19 a is later than the closing timing,(time t2)in a low-speed, low-load state and the level of lift of the intake valve19 a is set to L1, which is greater than the level of lift L3 in alow-speed, low-load state.

Then, in step s263J, the ECU 1 decides the amount of fuel injectionaccording to the amount of intake air controlled in step s267J and thetarget air-fuel ratio preset in the ECU 1 and injects fuel using thefuel injection valve 11.

Then, in step s270J, the ECU 1 reads the air-fuel ratio of thecombustion gas using the air-fuel ratio sensor 22 and feeds back theamount of new fuel injection and the amounts of operation of throttlevalve 7 and the variable valve mechanisms 15 a and 15 b of theintake/exhaust valves based on the output values thereof, and therebycontrols engine operation.

Then, in step s265J, the ECU 1 detects ignition timing based on theoutput value of the pressure sensor 27. Then, in step s270J2, the ECU 1compares the target ignition timing with the actual ignition timing andcontrols the throttle valve 7 and the variable valve mechanisms 15 a and15 b of the intake/exhaust valves so that the actual ignition timingcoincides with the target ignition timing. Here, the target ignitiontiming is preset in the ECU 1 as a value commensurate with the operatingcondition.

At this time, to prevent vibration, etc. in the engine, it is necessaryto control the output value of the air flow sensor 5 to a constant valueso that the amount of intake air does not change discontinuously duringoperation of the throttle valve 7 and the variable valve mechanisms 15 aand 15 b. This is because the amount of intake air or air-fuel ratiochanges drastically depending on time response of the variable valvemechanisms 15 a and 15 b, causing the operator to have uncomfortablefeeling or cause deterioration of exhaust due to accidental fire. Thatis, to keep normal operation of the engine against variations in theengine speed, it is necessary to perform concerted control between thethrottle valve 7 and variable valve mechanisms 15 a and 15 b asdescribed above.

As explained above, the embodiment can secure the amount of internal EGRand determine appropriate ignition timing using the variable valvemechanisms 15 a and 15 b and further correct the amount of intake airusing the throttle valve 7, and can thereby perform an optimum engineoperation according to the engine load and engine speed. Thus, theembodiment can expand the compression ignition combustion operatingarea.

Then, with reference now to FIG. 24 to FIG. 27, a configuration andoperation of a compression ignition internal combustion engine accordingto a third embodiment of the present invention will be explained below.

The configuration of the compression ignition internal combustion engineaccording to the embodiment is the same as that shown in FIG. 6. Theembodiment switches between a compression ignition combustion mode and aspark ignition combustion mode according to the engine speed and engineload.

FIG. 24 is a flow chart showing the contents of control of switchingbetween a compression ignition combustion mode and a spark ignitioncombustion mode of a compression ignition internal combustion engineaccording to a third embodiment of the present invention. Furthermore,FIG. 25 and FIG. 26 illustrate control of switching between acompression ignition combustion mode and a spark ignition combustionmode of the compression ignition internal combustion engine according tothe third embodiment of the present invention.

In step s200K, the ECU 1 starts operation mode switching control.

First, in step s210, the ECU 1 reads output values of the acceleratoropening detection device 2 a and the brake depressing force detectiondevice 2 b as the intention of the driver .

Then, in step s220, the ECU 1 takes in an output value of the vehiclespeed detection device 2 c as the vehicle driving condition and takes inoutput values of the accelerator opening detection device 2 a, theair-fuel ratio sensor 22, the crank angle sensor 4, the air flow sensor5 and the intake air temperature sensor mounted on the air flow sensor5, the engine cooling water temperature sensor 24 and the post-catalystexhaust temperature sensor 23 as the engine operating condition s.

Next, in step s225K, the ECU 1 decides whether it is necessary to changethe combustion state or not. If a change is necessary, the process moveson to step s261K.

Here, a relationship between the engine condition and the operation modewill be explained by using FIG. 25.

In FIG. 25, the horizontal axis shows an engine speed and the verticalaxis shows engine load. The compression ignition combustion area andspark ignition combustion area are predetermined by the engine speed andengine load, and these are stored in the ECU 1. In the illustratedexample, an area under a low-load, low-speed condition which correspondsto an idle rotation area corresponds to the spark ignition combustionarea and a high-load area also corresponds to the spark ignitioncombustion area. Other low-load areas correspond to compression ignitioncombustion operating areas.

For example, under an engine operating condition A with an engine speedof Ra and engine load of La, a spark ignition combustion is selected,while under an engine operating condition B with an engine speed of Rband engine load of Lb, a compression ignition combustion is selected.For example, the engine operating condition A corresponds to a conditionof driving on a flat ground and the engine operating condition Bcorresponds to a condition of driving on an ascending slope. Therefore,when the driving condition changes from a flat ground driving conditionto an ascending slope driving condition, it is necessary to switch theoperation mode from a compression ignition combustion mode to a sparkignition combustion mode.

When a combustion state needs to be changed, in step s261K, the ECU 1controls the amount of internal EGR through manipulation of the liftlevel of the exhaust valve. The internal EGR rate in the combustionchamber 16 differs drastically between a compression ignition combustionperiod and a spark ignition combustion period. For example, when acompression ignition combustion is switched to a spark ignitioncombustion between the condition A and condition B, the amount ofinternal EGR must be reduced drastically.

FIG. 26A illustrates an amount of air intake, FIG. 26B illustrates anarea of exhaust opening and FIG. 26C illustrates a change of an internalEGR rate when the engine operating condition changes from a point ofcondition A of a compression ignition combustion area to a point ofcondition B of the spark ignition combustion area. As shown in FIG. 26C,when a compression ignition combustion is switched to a spark ignitioncombustion between the condition A and condition B, the amount ofinternal EGR is reduced drastically at their switching point O. Toreduce the amount of internal EGR, the area of exhaust opening isincreased as shown in FIG. 26B. To increase the area of exhaust opening,the amount of trapping of internal EGR is reduced by increasing thelevel of lift or the level of lift and the valve opening time of theexhaust valve 19 b.

Then, in step s264K, the ECU 1 operates the throttle valve 7 andvariable valve mechanisms 15 a and 15 b to control the amount of intakeair. Here, if the amount of intake air changes, a torque variationoccurs, and therefore as shown in FIG. 26A, the opening of the throttlevalve 7 or the variable valve mechanisms 15 a and 15 b are controlled sothat the output value of the air flow sensor 5 does not changediscontinuously during switching between the combustion modes.

Next, in step s242K, the ECU 1 reads the amount of intake air from theoutput value of the air flow sensor 5. Then, in step s270K, the ECU 1performs feedback control so that the read amount of air reaches thetarget amount of air.

Here, an air-fuel ratio in the compression ignition combustion mode andspark ignition combustion mode of the compression ignition internalcombustion engine according to the third embodiment of the presentinvention will be explained by using FIG. 27.

FIG. 27 illustrates an air-fuel ratio in the compression ignitioncombustion mode and spark ignition combustion mode of the compressionignition internal combustion engine according to the third embodiment ofthe present invention.

In FIG. 27, the horizontal axis shows an engine speed and the verticalaxis shows an engine load. The compression ignition combustion area andthe spark ignition combustion area are predetermined by the engine speedand the engine load and stored in the ECU 1. In the illustrated example,an area under a low-load, low-speed condition which corresponds to anidle rotation area corresponds to the spark ignition combustion area anda high-load area also corresponds to the spark ignition combustion area.Other low-load areas correspond to the compression ignition operatingareas.

When the spark ignition combustion is selected as the combustion method,the compression ignition internal combustion engine of the embodimentoperates at a theoretical air-fuel ratio of the mixture or at anair-fuel ratio with more concentrated fuel. Furthermore, when thecompression ignition combustion is selected, it is possible to realize acombustion with ultra-low NOx and ultra-low HC through theaforementioned control. However, the exhaust level after an engineexhaust during the spark ignition combustion is almost no different fromthe exhaust level during an operation by the spark ignition combustionof the conventional engine and requires a cleanup of exhaust through acatalyst control. Thus, when the engine is operating under a sparkignition combustion, the compression ignition internal combustion engineof the embodiment performs engine operation at a theoretical air-fuelratio which corresponds to the best catalyst cleaning performance or atan air-fuel ratio with more concentrated fuel, and thereby realizes areduction of engine emissions in the spark ignition combustion area. Thepresent invention eliminates the need for a complicated catalystconfiguration for reducing engine emissions mounted on the conventionalengine and can provide a low-cost engine.

As shown above, at the time of switching the operation mode, theembodiment controls the amount of internal EGR using the variable valvemechanisms 15 a and 15 b and further corrects the amount of intake airthrough the throttle valve 7 and controls so that the amount of intakeair does not change drastically at a switching point 0, and can therebyreduce a torque variation accompanying switching between the operationmodes and realize smooth switching between operation modes.

Then, with reference now to FIG. 28, a configuration of a compressionignition internal combustion engine according to a fourth embodiment ofthe present invention will be explained.

FIG. 28 is a system block diagram showing a configuration of thecompression ignition internal combustion engine according to the fourthembodiment of the present invention. The same reference numerals asthose in FIG. 1 denote the same parts.

The embodiment is also provided with a bypass flow rate control device30 in addition to the throttle valve 7 shown in FIG. 1 as a intake airregulating device. The bypass flow rate control device 30 consists of abypass flow channel 30 a that connects the upstream and downstream ofthe throttle valve 7 and a valve 30 b provided inside this bypass flowchannel 30 a. The valve 30 b whose opening is controlled by the ECU 1controls the amount of micro intake air that flows through the bypassflow channel 30 a.

As explained in FIG. 15 to FIG. 17, when the engine operates under arelatively low-load, low-speed rotation condition, if the amount of airrequired for the engine is relatively small, it is possible toaccurately control the micro intake air flow rate by closing thethrottle valve 7 and controlling the micro air flow rate through thebypass flow rate control device 30.

Even under a low-load, low-speed condition, the embodiment canaccurately control the micro air flow rate and accurately control acompression ignition combustion.

Then, a configuration of a compression ignition internal combustionengine according to a fifth embodiment of the present invention will beexplained by using FIG. 29.

FIG. 29 is a system block diagram showing a configuration of thecompression ignition internal combustion engine according to the fifthembodiment of the present invention. The same reference numerals asthose in FIG. 1 denote the same parts.

The embodiment is also provided with a supercharging air flow ratecontrol device 32 in addition to the throttle valve 7 shown in FIG. 1 asa intake air regulating device. The supercharging air flow rate controldevice 32 consists of a supercharger 32 a provided on the upstream sideof the throttle valve 7, a bypass flow channel 32 b that connects theupstream and downstream of this supercharger 32 a and a valve 32 cprovided inside this bypass flow channel 32 b. A supercharge of thesupercharger 32 a is controlled by the ECU 1. The valve 32 c whoseopening is controlled by the ECU 1 controls the intake air flow rateflowing through the bypass flow channel 32 b.

When the engine operates under a high-load, high-speed rotationcondition, if the internal EGR is used to control the temperature of themixture in the combustion chamber 16, the required amount of intake airmay be insufficient through only normal control of the throttle valve 7.Thus, the embodiment provides the supercharging air flow rate controldevice 32 on the upstream side of the throttle valve 7 and allows theECU 1 to control the flow rate control device 32 according to theintention of the driver, vehicle driving condition and the engineoperating condition, and can thereby control the amount of intake air.

A pressure in the combustion chamber at the beginning compression and acompression ignition timing have such a relationship that an ignitiontiming can be advanced when the pressure in the combustion chamber ishigh, while the ignition timing is delayed when the pressure in thecombustion chamber is low. Thus, the ECU 1 controls the superchargingair flow rate control device 32 and can thereby control the compressionignition timing of the engine.

Even under a high-load, high-speed condition, the embodiment can supplya required amount of air and also control a compression ignition timingas well.

Then, a configuration of a compression ignition internal combustionengine according to a sixth embodiment of the present invention will beexplained by using FIG. 30.

FIG. 30 is a system block diagram showing a configuration of thecompression ignition internal combustion engine according to the sixthembodiment of the present invention. The same reference numerals asthose in FIG. 1 denote the same parts.

The embodiment is provided with a path 40 and a valve 42 as a intake airregulating device. The path 40 is a bypass for an external EGR providedby connecting the exhaust path 14 and intake path 6 and returns anexhaust gas in the exhaust path 14 to the intake path 6. The valve 42 iscontrolled by the ECU 1 and controls the flow rate of the returnedexhaust gas. That is, provision of the path 40 as the bypass forexternal EGR combined with the use of the internal EGR allows control ofignition and combustion. The ECU 1 changes the opening of the valve 42according to the operating condition, vehicle driving condition andintention of the driver and thereby controls the amount of external EGR.External EGR does not hold a heat value as high as that of internal EGRand has highly concentrated inert chemical species that extends theperiod of combustion such as CO2, and therefore if the ignition timingshould be delayed or the combustion period should be extended, it ispossible to perform such control that increases the flow rate ofexternal EGR.

The embodiment can control not only the amount of external EGR but alsoignition and combustion.

Then, a compression ignition internal combustion engine according to aseventh embodiment of the present invention will be explained by usingFIG. 31 to FIG. 33. The system configuration showing a configuration ofthe compression ignition internal combustion engine according to theembodiment is the same as that shown in FIG. 1. Furthermore, the methodof deciding the combustion mode of the compression ignition internalcombustion engine according to the embodiment is the same as that in theflow chart shown in FIG. 2.

The embodiment will explain a specific example of the method of decidinga combustion method whether the compression ignition combustion mode orthe spark ignition combustion mode in step s160 in FIG. 2. Theembodiment selects the compression ignition combustion mode or the sparkignition combustion mode based on the accelerator opening and vehicleacceleration.

FIG. 31 shows an operating area map to determine a combustion method inthe compression ignition internal combustion engine according to theseventh embodiment of the present invention, FIG. 32 illustrates a heatgeneration curve and FIG. 33 is a flow chart showing an operation of thecompression ignition internal combustion engine according to the seventhembodiment of the present invention when compression ignition isprohibited.

In step s160 in FIG. 2, the ECU 1 decides a combustion method, whether acompression ignition combustion mode or a spark ignition combustion modebased on the output values of each sensor and the detecting means readin steps silo to s150. At this time, the ECU 1 decides the combustionmethod with reference to the operating area map shown in FIG. 31.

As shown in FIG. 31, an operating area Z1 where the accelerator openingis equal to or greater than a predetermined value or where the (absolutevalue of) acceleration of the vehicle is equal to or greater than apredetermined value corresponds to a spark ignition combustion zone.Furthermore, an operating area Z2 where the accelerator opening is equalto or smaller than a predetermined value and where the (absolute valueof) acceleration of the vehicle is equal to or smaller than apredetermined value corresponds to a compression ignition combustionzone. By the way, an operating area Z3 where the accelerator opening isequal to or smaller than a predetermined value and where the (absolutevalue of) acceleration of the vehicle is equal to or greater than apredetermined value corresponds to a compression ignition combustionprohibition zone, which will be described later by using FIG. 33.

FIG. 32 shows a heat generation rate curve with the horizontal axisshowing a crank angle. A compression ignition combustion is known to bea self-ignition combustion that takes place at multiple pointssimultaneously, and therefore the compression ignition combustion hasdifficulty in controlling ignition and has a heat generation periodshorter than that of a spark ignition combustion as shown in FIG. 32.Furthermore, the compression ignition combustion has specific naturethat even if its air-fuel ratio of the mixture can be brought closer toa theoretical air-fuel ratio, the peak of heat generation increases butthe combustion period hardly changes, and therefore a drastic pressurerise is accompanied by slapping sound, which makes a stable operation ofthe engine difficult.

Thus, as shown in FIG. 31, for the operating area Z1, for reasons thatgreater torque than that during steady driving is required and it isdifficult to perform a stable compression ignition combustion operationbecause an engine operating condition changes drastically, etc., a sparkignition combustion is selected to avoid abrupt heat generation andrealize a moderate engine operation. On the other hand, for theoperating area Z2, a compression ignition combustion is selected.

Then, control of the operating area Z3 where the accelerator opening isequal to or smaller than a predetermined value and where the (absolutevalue of) acceleration of the vehicle is equal to or greater than apredetermined value will be explained by using FIG. 33.

First, in step s410, the ECU 1 reads the output value of the acceleratoropening detection device 2 a as the intention of the driver.

Then, in step s420, the ECU 1 takes in the output value of the vehiclespeed detection device 2 c as the vehicle driving condition and takes inthe output values of the accelerator opening detection device 2 a, theair-fuel ratio sensor 22, the crank angle sensor 4, the air flow sensor5 and the intake air temperature sensor mounted on the air flow sensor5, the engine cooling water temperature sensor 24 and the post-catalystexhaust temperature sensor 23 as the engine operating conditions.

Next, in step s430, the ECU 1 decides whether the accelerator openingread in step s410 is equal to or smaller than a predetermined value ornot and whether the (absolute value of) vehicle acceleration is equal toor greater than a predetermined value or not and if the value is equalto or smaller than a predetermined value, the ECU 1 moves on to steps440.

When the accelerator opening is equal to or smaller than a predeterminedvalue, in step s440, the ECU 1 decides whether the compression ignitioncombustion is in progress or not, and the ECU 1 moves on to step s470 ifthe compression ignition combustion is in progress or step s450otherwise.

If the compression ignition combustion is not in progress, in step s450,the ECU 1 decides whether the spark ignition combustion is in progressor not, and if the spark ignition combustion is in progress, the ECU 1moves on to step s460.

Then, in step s460, the ECU 1 shuts off an ignition signal and prohibitsspark ignition.

Furthermore, in step s470, the ECU 1 stops fuel injection.

Thus, when the accelerator opening is equal to or smaller than apredetermined value and the (absolute value of) vehicle acceleration isequal to or greater than a predetermined value, the required torque ofthe engine is zero or minus, and therefore the ECU 1 sends a command toprohibit the compression ignition combustion and shuts off the ignitionsignal or stops fuel injection. This allows extra fuel consumption to besuppressed, thus reducing HC emissions and fuel consumption.

Furthermore, when the vehicle speed is kept to a predetermined value orhigher and when it is decided that the driver of the vehicle has steppedon the accelerator again, the ECU 1 restarts fuel injection and commandsfor the compression ignition or the spark ignition operation mode basedon the intention of the driver, vehicle driving condition, engineoperating condition and various sensor values. That is, the embodimentsuppresses extra fuel consumption by the engine and allows smoothvehicle driving.

When the required torque of the engine is zero or minus, the embodimentcan stop fuel injection and reduce both HC emissions and fuelconsumption.

Then, a compression ignition internal combustion engine according to aneighth embodiment of the present invention will be explained by usingFIG. 34 and FIG. 35. The system configuration showing a configuration ofthe compression ignition internal combustion engine according to theembodiment is the same as that shown in FIG. 1. Furthermore, the methodof deciding the combustion mode of the compression ignition internalcombustion engine according to the embodiment is the same as that in theflow chart shown in FIG. 2.

The embodiment will explain another specific example of the method ofdeciding the combustion method, whether the compression ignitioncombustion mode or the spark ignition combustion mode in step s160 inFIG. 2. The embodiment selects the compression ignition combustion modeor the spark ignition combustion mode based on the accelerator openingand vehicle speed.

FIG. 34 shows an operating area map to determine a combustion method inthe compression ignition internal combustion engine according to theeighth embodiment of the present invention and FIG. 35 is a flow chartshowing an operation of the compression ignition internal combustionengine of the eighth embodiment of the present invention whencompression ignition is prohibited.

In step s160 in FIG. 2, the ECU 1 decides the combustion method, whetherthe compression ignition combustion mode or the spark ignitioncombustion mode based on the output values of each sensor and thedetecting means read in steps s110 to s150. At this time, the ECU 1decides the combustion method with reference to the operating area mapshown in FIG. 34.

As shown in FIG. 34, an operating area Z4 where the accelerator openingis equal to or greater than a predetermined value or where the vehiclespeed is equal to or greater than a predetermined value corresponds to aspark ignition combustion zone. Furthermore, an operating area Z5 wherethe accelerator opening is equal to or smaller than a predeterminedvalue and where the vehicle speed is equal to or smaller than apredetermined value corresponds to a compression ignition combustionzone. By the way, an operating area Z6 where the accelerator opening isequal to or smaller than a predetermined value and where the vehiclespeed is equal to or greater than a predetermined value corresponds to acompression ignition combustion prohibition zone, which will bedescribed later using FIG. 35.

As shown in FIG. 34, for the operating area Z4, for reasons that greatertorque than that during steady driving is required and it is difficultto perform a stable compression ignition combustion operation because anengine operating condition changes drastically, etc., a spark ignitioncombustion is selected to avoid abrupt heat generation and realize amoderate engine operation. Then, for the operating area Z5, acompression ignition combustion is selected.

Then, control of the operation Z5 where the accelerator opening is equalto or smaller than a predetermined value will be explained by using FIG.35.

First, in step s410, the ECU 1 reads the output value of the acceleratoropening detection device 2 a as the intention of the driver.

Then, in step s420, the ECU 1 takes in the output value of the vehiclespeed detection device 2 c as the vehicle driving condition and takes inthe output values of the accelerator opening detection device 2 a, theair-fuel ratio sensor 22, the crank angle sensor 4, the air flow sensor5 and the intake air temperature sensor mounted on the air flow sensor5, the engine cooling water temperature sensor 24 and the post-catalystexhaust temperature sensor 23 as the engine operating conditions.

Next, in step s430A, the ECU 1 decides whether the accelerator openingread in step s410 is equal to or smaller than a predetermined value ornot and whether the vehicle speed is equal to or greater than apredetermined value or not. If this condition is satisfied, the ECU 1moves on to step s440.

When the accelerator opening is equal to or smaller than a predeterminedvalue and the vehicle speed is equal to or greater than a predeterminedvalue, in step s440, the ECU 1 decides whether the compression ignitioncombustion is in progress or not, and the ECU 1 moves on to step s470 ifthe compression ignition combustion is in progress or step s450otherwise.

If the compression ignition combustion is not in progress, in step s450,the ECU 1 decides whether the spark ignition combustion is in progressor not, and if the spark ignition combustion is in progress, the ECU 1moves on to step s460.

Then, in step s460, the ECU 1 shuts off an ignition signal and prohibitsspark ignition.

Furthermore, in step s470, the ECU 1 stops fuel injection.

Thus, when the accelerator opening is equal to or smaller than apredetermined value and the vehicle speed is equal to or greater than apredetermined value, it is such a condition that the vehicle is drivingon a descending slope and the required torque of the engine is zero orminus, and therefore the ECU 1 sends a command to prohibit a compressionignition combustion and shuts off the ignition signal or stops fuelinjection. This allows extra fuel consumption to be suppressed, thusreducing HC emissions and fuel consumption.

When the required torque of the engine is zero or minus, the embodimentcan stop fuel injection and reduce both HC emissions and fuelconsumption.

Then, a compression ignition internal combustion engine according to aninth embodiment of the present invention will be explained by usingFIG. 36. The system configuration showing a configuration of thecompression ignition internal combustion engine according to theembodiment is the same as that shown in FIG. 1. Furthermore, the methodof deciding a combustion mode of the compression ignition internalcombustion engine according to the embodiment is the same as that in theflow chart shown in FIG. 2.

The embodiment will explain another specific example of the content ofcontrol when the driver of the vehicle incorporating the compressionignition internal combustion engine steps on the brake during driving.

FIG. 36 is a flow chart showing an operation of the compression ignitioninternal combustion engine according to the ninth embodiment of thepresent invention when compression ignition is prohibited.

First, in step s410, the ECU 1 reads the output value of the brakedepressing force detection device 2 b as the intention of the driver.

Then, in step s420, the ECU 1 takes in the output value of the vehiclespeed detection device 2 c as the vehicle driving condition and takes inthe output values of the accelerator opening detection device 2 a, theair-fuel ratio sensor 22, the crank angle sensor 4, the air flow sensor5 and the intake air temperature sensor mounted on the air flow sensor5, the engine cooling water temperature sensor 24 and the post-catalystexhaust temperature sensor 23 as the engine operating conditions.

Next, in step s430B, the ECU 1 decides whether the brake depressingforce read in step s410 is equal to or greater than a predeterminedvalue or not and whether the vehicle speed is equal to or greater than apredetermined value or not. If this condition is satisfied, the ECU 1moves on to step s440.

When the brake depressing force is equal to or greater than apredetermined value and the vehicle speed is equal to or greater than apredetermined value, in step s440, the ECU 1 decides whether acompression ignition combustion is in progress or not, and the ECU 1moves on to step s470 if a compression ignition combustion is inprogress or step s450 otherwise.

If a compression ignition combustion is not in progress, in step s450,the ECU 1 decides whether the spark ignition combustion is in progressor not, and if the spark ignition combustion is in progress, the ECU 1moves on to step s460.

Then, in step s460, the ECU 1 shuts off an ignition signal and prohibitsspark ignition.

Furthermore, in step s470, the ECU 1 stops fuel injection.

When the driver who drives the vehicle attempts to decelerate from anormal driving condition, the driver removes his/her foot from theaccelerator and steps on the brake. In this case, if the brakedepressing force is equal to or greater than a predetermined value, thisindicates that the driver of the vehicle incorporating the engine needsan appropriate brake force, and therefore it is necessary to apply anegative pressure to the inside of the intake port 6 to assist the brakeand reduce the opening of the throttle valve 7 to almost full closing.Furthermore, the target drive force in this case is zero or minus, andtherefore the ECU 1 sends a command to prohibit a compression ignitioncombustion and shuts off the ignition signal or stops fuel injection.This allows extra fuel consumption to be suppressed, thus reducing HCemissions and fuel consumption.

Furthermore, when the vehicle speed is kept to a predetermined value orgreater and it is decided that the driver of the vehicle has stepped onthe accelerator again, the ECU 1 restarts fuel injection and commandsfor the compression ignition or the spark ignition operation mode basedon the intention of the driver, the vehicle driving condition, theengine operating condition and the various sensor values. That is, theembodiment suppresses extra fuel consumption by the engine and allowssmooth vehicle driving.

When the required torque of the engine is zero or minus, the embodimentcan stop fuel injection and reduce both HC emissions and fuelconsumption.

Then, a compression ignition internal combustion engine according to atenth embodiment of the present invention will be explained by usingFIG. 37 and FIG. 39.

First, the configuration of the compression ignition internal combustionengine according to the embodiment will be explained by using FIG. 37.

FIG. 37 is a system block diagram showing a configuration of thecompression ignition internal combustion engine according to the tenthembodiment of the present invention. In FIG. 37, the same referencenumerals as those in FIG. 1 denote the same parts.

In addition to the configuration shown in FIG. 1, the embodiment isfurther provided with a temperature sensor 44 in the exhaust port 14.The temperature sensor 44 is used to detect temperature of the exhaustgas. The output value of the temperature sensor 44 is taken into the ECU1.

Then, the method of deciding a combustion mode in the compressionignition internal combustion engine according to the embodiment will beexplained by using FIG. 38.

FIG. 38 is a flow chart showing the method of deciding a combustion modein the compression ignition internal combustion engine according to thetenth embodiment of the present invention.

When the ECU 1 starts an engine start control, first, in step s105, theECU 1 reads a cooling water temperature which is the output of theengine cooling water temperature sensor 24 and intake air temperaturedetected by the air flow sensor 5 as the engine operating conditions.

Then, in step s165, the ECU 1 decides whether the cooling water orintake air temperature read in step s105 is equal to or lower than apredetermined value or not, and if it is equal to or lower than apredetermined value, the ECU 1 moves on to step s300 and starts tocontrol a spark ignition combustion mode. Furthermore, if the readcooling water or intake air temperature is greater than a predeterminedvalue, the ECU 1 moves on to step s200 and starts to control acompression ignition combustion mode.

Ignition timings in a compression ignition combustion mode stronglydepend on parameters such as a temperature, pressure and air-fuel ratioand in the case where the temperature of the engine is low as in thecase of a cold start and each measuring sensor has not started tofunction yet and it is difficult to calculate the amount of air, it isextremely difficult to control ignition timings and a combustion period,or fully control the output torque of the engine. Thus, in the case ofsuch a cold start where either the cooling water temperature or intakeair temperature of the engine is equal to or lower than a predeterminedvalue, selecting a spark ignition combustion makes it possible torealize a smooth engine start.

Then, a method of controlling switching between combustion modes of thecompression ignition internal combustion engine according to theembodiment will be explained by using FIG. 39.

FIG. 39 is a flow chart showing a combustion mode switching controlmethod of the compression ignition internal combustion engine accordingto the tenth embodiment of the present invention.

In step s500, the ECU 1 starts a combustion switching control routineafter the engine is started.

First, in step s510, the ECU 1 reads output values of the acceleratoropening detection device 2 a and the brake depressing force detectiondevice 2 b as the intention of the driver.

Then, in step s520, the ECU 1 takes in an output value of vehicle speeddetection device 2 c as the vehicle driving condition and takes inoutput values of the accelerator opening detection device 2 a, theair-fuel ratio sensor 22, the crank angle sensor 4, the air flow sensor5 and the intake air temperature sensor mounted on the air flow sensor5, the engine cooling water temperature sensor 24 and the post-catalystexhaust temperature sensor 23 as the engine operating conditions.

Then, in step s530, the ECU 1 decides whether the cooling watertemperature or intake air temperature is equal to or greater than apredetermined value or not based on the information read in steps s210to s220 and if both are equal to or greater than a predetermined value,the ECU 1 moves on to step s560. If not, the ECU 1 moves on to step s550and decides whether the output of the exhaust temperature sensor isequal to or greater than a predetermined value and if it is equal to orgreater than a predetermined value, the ECU 1 moves on to step s560.

Then, when: the cooling water temperature and intake air temperaturebecome equal to or greater than a predetermined value or when the outputvalue of the temperature sensor 44 becomes equal to or greater than apredetermined value, in step s560, ECU 1 switches from a spark ignitioncombustion to compression ignition combustion because an initialtemperature in the combustion chamber 16 at the start of a compression,that is, at timing at which the intake valve 19 a closes is secured byan amount necessary for ignition. At this time, it is also possible touse the output value of the post-catalyst exhaust temperature sensor 23instead of the output value of the temperature sensor 44, and using thisoutput value makes it possible to decide whether a compression startingtemperature enough to start ignition has been secured or not.

The embodiment makes it possible to select a combustion mode accordingto a cooling water temperature or exhaust temperature at the start ofthe engine and improve a starting characteristic, and after the engineis started, immediately start the compression ignition combustion modeif conditions are ready.

As described above, the compression ignition internal combustion enginedescribed in the aforementioned embodiments is an engine system thatmakes compatible a self-ignition combustion with a spark ignitioncombustion and can control an amount of internal EGR, amount of intakeair and compression ignition timings independently by controlling theintake air regulating device and the variable valve mechanisms accordingto the intention of the driver, vehicle driving condition and engineoperating condition. That is, the present invention has excellentadvantages of making compatible an increase in a compressionself-ignition operating area with an optimum output torque control inthis operating area and also smoothly switching between a self-ignitioncombustion and a spark ignition combustion, and can thereby realize lowNOx and low HC fuel consumption.

INDUSTRIAL APPLICABILITY

The present invention makes compatible an increase in compressionself-ignition operating area with an optimum output torque control inthis operating area and also smoothly switches a self-ignitioncombustion and a spark ignition combustion.

What is claimed is:
 1. A compression ignition internal combustion enginefor operating by switching a spark ignition combustion using an ignitiondevice and a compression ignition combustion for self-igniting a mixtureby piston compression comprising: variable valve mechanisms for varyingat least one of valve timings and valve lifts of an intake valve and anexhaust valve; intake air regulating means for varying an amount of airintake into a combustion chamber on an upstream side of a combustionchamber inlet of the compression ignition internal combustion engine;and control means for controlling said variable valve mechanisms andsaid intake air regulating means during a compression ignitioncombustion so as to perform a compression ignition combustion; whereinsaid control means controls said variable valve mechanisms so as toreduce valve lifts of said exhaust valve during a compression ignitioncombustion.
 2. A compression ignition internal combustion engine foroperating by switching a spark ignition combustion using an ignitiondevice and a compression ignition combustion for self-igniting a mixtureby piston compression comprising: variable valve mechanisms for varyingat least one of valve timings and valve lifts of an intake valve and anexhaust valve; intake air regulating means for varying an amount of airintake into a combustion chamber on an upstream side of a combustionchamber inlet of the compression ignition internal combustion engine;and control means for controlling said variable valve mechanisms andsaid intake air regulating means during a compression ignitioncombustion so as to perform a compression ignition combustion; whereinsaid control means decides an amount of fuel injection according toengine operating conditions of said compression ignition internalcombustion engine, a vehicle driving condition of a vehicleincorporating said compression ignition internal combustion engine andan intention of a driver of said vehicle incorporating said compressionignition internal combustion engine, calculates a target amount ofintake air from said decided amount of fuel injection so as to attain atarget air-fuel ratio and controls said variable valve mechanisms andsaid intake air regulating means so that the amount of air intake intosaid combustion chamber becomes the target amount of air.
 3. Acompression ignition internal combustion engine for operating byswitching a spark ignition combustion using an ignition device and acompression ignition combustion for self-igniting a mixture by pistoncompression comprising: variable valve mechanisms for varying at leastone of valve timings and valve lifts of an intake valve and an exhaustvalve; intake air regulating means for varying an amount of air intakeinto a combustion chamber on an upstream side of a combustion chamberinlet of the compression ignition internal combustion engine; andcontrol means for controlling said variable valve mechanisms and saidintake air regulating means during a compression ignition combustion soas to perform a compression ignition combustion; wherein said controlmeans decides an amount of fuel injection according to engine operatingconditions of said compression ignition internal combustion engine, avehicle driving condition of a vehicle incorporating said compressionignition internal combustion engine and an intention of a driver of saidvehicle incorporating said compression ignition internal combustionengine, calculates a target amount of intake air from said decidedamount of fuel injection so as to attain a target air-fuel ratio andcontrols said variable valve mechanisms and said intake air regulatingmeans so that an ignition timing becomes a target ignition timing.
 4. Acompression ignition internal combustion engine for operating byswitching a spark ignition combustion using an ignition device and acompression ignition combustion for self-igniting a mixture by pistoncompression comprising: variable valve mechanisms for varying at leastone of valve timings and valve lifts of an intake valve and an exhaustvalve; intake air regulating means for varying an amount of air intakeinto a combustion chamber on an upstream side of a combustion chamberinlet of the compression ignition internal combustion engine; andcontrol means for controlling said variable valve mechanisms and saidintake air regulating means during a compression ignition combustion soas to perform a compression ignition combustion; wherein said controlmeans decides a target amount of intake air according to engineoperating conditions of said compression ignition internal combustionengine, a vehicle driving condition of a vehicle incorporating saidcompression ignition internal combustion engine and an intention of adriver of said vehicle incorporating said compression ignition internalcombustion engine and controls said variable valve mechanisms and saidintake air regulating means so that an air-fuel ratio becomes a targetair-fuel ratio.
 5. A compression ignition internal combustion engineaccording to claim 4, wherein said control means further performsfeedback control so that an ignition timing becomes a target ignitiontiming.
 6. A compression ignition internal combustion engine foroperating by switching a spark ignition combustion using an ignitiondevice and a compression ignition combustion for self-igniting a mixtureby piston compression comprising: variable valve mechanisms for varyingat least one of valve timings and valve lifts of an intake valve and anexhaust valve; intake air regulating means for varying an amount of airintake into a combustion chamber on an upstream side of a combustionchamber inlet of the compression ignition internal combustion engine;and control means for controlling said variable valve mechanisms andsaid intake air regulating means during a compression ignitioncombustion so as to perform a compression ignition combustion; whereinsaid control means operates said intake valve or said exhaust valveaccording to engine operating conditions of said compression ignitioninternal combustion engine, a vehicle driving condition of a vehicleincorporating said compression ignition internal combustion engine andan intention of a driver of said vehicle incorporating said compressionignition internal combustion engine and controls fuel injecting meansand said intake air regulating means so that an air-fuel ratio becomes atarget air-fuel ratio.
 7. A compression ignition internal combustionengine according to claim 6, wherein said control means further performsfeedback control so that an ignition timing becomes a target ignitiontiming.
 8. A compression ignition internal combustion engine foroperating by switching a spark ignition combustion using an ignitiondevice and a compression ignition combustion for self-igniting a mixtureby piston compression comprising: variable valve mechanisms for varyingat least one of valve timings and valve lifts of an intake valve and anexhaust valve; intake air regulating means for varying an amount of airintake into a combustion chamber on an upstream side of a combustionchamber inlet of the compression ignition internal combustion engine;and control means for controlling said variable valve mechanisms andsaid intake air regulating means during a compression ignitioncombustion so as to perform a compression ignition combustion; whereinsaid control means controls said variable valve mechanisms, said fuelinjecting means and said intake air regulating means according to engineoperating conditions of said compression ignition internal combustionengine, a vehicle driving condition of a vehicle incorporating saidcompression ignition internal combustion engine and an intention of adriver of the vehicle incorporating said compression ignition internalcombustion engine so that an air-fuel ratio becomes a target air-fuelratio.
 9. A compression ignition internal combustion engine according toclaim 8, wherein said control means performs feedback control so that anignition timing becomes a target ignition timing.
 10. A compressionignition internal combustion engine for operating by switching a sparkignition combustion using an ignition device and a compression ignitioncombustion for self-igniting a mixture by piston compression comprising:variable valve mechanisms for varying at least one of valve timings andvalve lifts of an intake valve and an exhaust valve; intake airregulating means for varying an amount of air intake into a combustionchamber on an upstream side of a combustion chamber inlet of thecompression ignition internal combustion engine; and control means forcontrolling said variable valve mechanisms and said intake airregulating means during a compression ignition combustion so as toperform a compression ignition combustion; wherein said control meansoperates said intake air regulating means according to engine operatingconditions of said compression ignition internal combustion engine, avehicle driving condition of a vehicle incorporating said compressionignition internal combustion engine and an intention of a driver of saidvehicle incorporating said compression ignition internal combustionengine and controls said fuel injecting means and said variable valvemechanisms so that an air-fuel ratio becomes a target air-fuel ratio.11. A compression ignition internal combustion engine according to claim10, wherein said control means further performs feedback control so thatan ignition timing coincides with a target ignition timing.
 12. Acompression ignition internal combustion engine for operating byswitching a spark ignition combustion using an ignition device and acompression ignition combustion for self-igniting a mixture by pistoncompression comprising: variable valve mechanisms for varying at leastone of valve timings and valve lifts of an intake valve and an exhaustvalve; intake air regulating means for varying an amount of air intakeinto a combustion chamber on an upstream side of a combustion chamberinlet of the compression ignition internal combustion engine; andcontrol means for controlling said variable valve mechanisms and saidintake air regulating means during a compression ignition combustion soas to perform a compression ignition combustion; wherein said controlmeans controls said variable valve mechanisms so that the intake valvehas small lifts and the closing timing of the intake valve is advancedduring an operating condition is in a low-speed and low-load state. 13.A compression ignition internal combustion engine according to claim 12,wherein said control means maximizes an amount of intake air by saidintake air regulating means while keeping an internal EGR rate constant.14. A compression ignition internal combustion engine for operating byswitching a spark ignition combustion using an ignition device and acompression ignition combustion for self-igniting a mixture by pistoncompression comprising: variable valve mechanisms for varying at leastone of valve timings and valve lifts of an intake valve and an exhaustvalve; intake air regulating means for varying an amount of air intakeinto a combustion chamber on an upstream side of a combustion chamberinlet of the compression ignition internal combustion engine; andcontrol means for controlling said variable valve mechanisms and saidintake air regulating means during a compression ignition combustion soas to perform a compression ignition combustion; wherein said controlmeans controls said variable valve mechanisms or said intake airregulating means so that a temperature of a mixture inside saidcombustion chamber increases at the start of a compression process as anengine speed increases in an operating area by said compression ignitioncombustion so as to increase an internal EGR rate.
 15. A compressionignition internal combustion engine for operating by switching a sparkignition combustion using an ignition device and a compression ignitioncombustion for self-igniting a mixture by piston compression comprising:variable valve mechanisms for varying at least one of valve timings andvalve lifts of an intake valve and an exhaust valve; intake airregulating means for varying an amount of air intake into a combustionchamber on an upstream side of a combustion chamber inlet of thecompression ignition internal combustion engine; and control means forcontrolling said variable valve mechanisms and said intake airregulating means during a compression ignition combustion so as toperform a compression ignition combustion; wherein said control meanscontrols so that an amount of fuel injection increases as an enginespeed increases in an operating area by said compression ignitioncombustion.
 16. A compression ignition internal combustion engine foroperating by switching a spark ignition combustion using an ignitiondevice and a compression ignition combustion for self-igniting a mixtureby piston compression comprising: variable valve mechanisms for varyingat least one of valve timings and valve lifts of an intake valve and anexhaust valve; intake air regulating means for varying an amount of airintake into a combustion chamber on an upstream side of a combustionchamber inlet of the compression ignition internal combustion engine;and control means for controlling said variable valve mechanisms andsaid intake air regulating means during a compression ignitioncombustion so as to perform a compression ignition combustion; whereinsaid control means controls so that an air-fuel ratio approaches atheoretical air-fuel ratio as an engine speed increases in an operatingarea by said compression ignition combustion.
 17. A compression ignitioninternal combustion engine for operating by switching a spark ignitioncombustion using an ignition device and a compression ignitioncombustion for self-igniting a mixture by piston compression comprising:variable valve mechanisms for varying at least one of valve timings andvalve lifts of an intake valve and an exhaust valve; intake airregulating means for varying an amount of air intake into a combustionchamber on an upstream side of a combustion chamber inlet of thecompression ignition internal combustion engine; and control means forcontrolling said variable valve mechanisms and said intake airregulating means during a compression ignition combustion so as toperform a compression ignition combustion; wherein when said compressionignition combustion is switched to said spark ignition combustion, saidcontrol means controls said variable valve mechanisms so that aninternal EGR rate is reduced compared with that during said compressionignition combustion.
 18. A compression ignition internal combustionengine according to claim 17, wherein when said compression ignitioncombustion is switched to said spark ignition combustion, said controlmeans controls said intake air regulating means so that an amount ofintake air changes continuously.
 19. A compression ignition internalcombustion engine for operating by switching a spark ignition combustionusing an ignition device and a compression ignition combustion forself-igniting a mixture by piston compression comprising: variable valvemechanisms for varying at least one of valve timings and valve lifts ofan intake valve and an exhaust valve; intake air regulating means forvarying an amount of air intake into a combustion chamber on an upstreamside of a combustion chamber inlet of the compression ignition internalcombustion engine; and control means for controlling said variable valvemechanisms and said intake air regulating means during a compressionignition combustion so as to perform a compression ignition combustion;wherein said intake air regulating means is provided in a flow channelthat bypasses an intake path.
 20. A compression ignition internalcombustion engine for operating by switching a spark ignition combustionusing an ignition device and a compression ignition combustion forself-igniting a mixture by piston compression comprising: variable valvemechanisms for varying at least one of valve timings and valve lifts ofan intake valve and an exhaust valve; intake air regulating means forvarying an amount of air intake into a combustion chamber on an upstreamside of a combustion chamber inlet of the compression ignition internalcombustion engine; and control means for controlling said variable valvemechanisms and said intake air regulating means during a compressionignition combustion so as to perform a compression ignition combustion;wherein said intake air regulating means is provided by a superchargerwhich supplies supercharged air into said combustion chamber and saidcontrol means controls the amount of air to be supplied by controllingthe supercharging pressure of this supercharger.
 21. A compressionignition internal combustion engine for operating by switching a sparkignition combustion using an ignition device and a compression ignitioncombustion for self-igniting a mixture by piston compression comprising:variable valve mechanisms for varying at least one of valve timings andvalve lifts of an intake valve and an exhaust valve; intake airregulating means for varying an amount of air intake into a combustionchamber on an upstream side of a combustion chamber inlet of thecompression ignition internal combustion engine; and control means forcontrolling said variable valve mechanisms and said intake airregulating means during a compression ignition combustion so as toperform a compression ignition combustion; wherein said control meanscontrols for switching said spark ignition combustion and saidcompression ignition combustion according to engine operating conditionsof this compression ignition internal combustion engine, a vehicledriving condition of said vehicle incorporating said compressionignition internal combustion engine and an intention of a driver of saidvehicle incorporating said compression ignition internal combustionengine.
 22. A compression ignition internal combustion engine accordingto claim 21, wherein when an accelerator opening is equal to or greaterthan a predetermined value or when a vehicle acceleration is equal to orgreater than a predetermined value, said engine is operated by saidspark ignition combustion.
 23. A compression ignition internalcombustion engine according to claim 21, wherein when an acceleratoropening is equal to or greater than a predetermined value or when thevehicle speed is equal to or greater than a predetermined value, saidengine is operated by said spark ignition combustion.
 24. A compressionignition internal combustion engine according to claim 21, wherein whena vehicle speed is equal to or greater than a predetermined value and abrake depressing force is equal to or greater than a predeterminedvalue, engine operation by said compression ignition combustion isprohibited.
 25. A compression ignition internal combustion engineaccording to claim 21, wherein when a cooling water temperature and a anintake air temperature are equal to or lower than a predetermined value,said engine is operated by said spark ignition combustion.
 26. Acompression ignition internal combustion engine according to claim 25,wherein when an exhaust temperature is equal to or higher than apredetermined value, engine operation is switched to operation by saidcompression ignition combustion.
 27. A compression ignition internalcombustion engine for operating by switching a spark ignition combustionusing an ignition device and a compression ignition combustion forself-igniting a mixture by piston compression comprising: variable valvemechanisms for varying at least one of valve timings and valve lifts ofan intake valve and an exhaust valve; intake air regulating means forvarying an amount of air intake into a combustion chamber on an upstreamside of a combustion chamber inlet of the compression ignition internalcombustion engine; and control means for controlling said variable valvemechanisms and said intake air regulating means during a compressionignition combustion so as to perform a compression ignition combustion;wherein said control means prohibits engine operation by saidcompression ignition combustion according to engine operating conditionsof said compression ignition internal combustion engine, a vehicledriving condition of a vehicle incorporating said compression ignitioninternal combustion engine and an intention of a driver of the vehicleincorporating said compression ignition internal combustion engine. 28.A compression ignition internal combustion engine for operating byswitching a spark ignition combustion using an ignition device and acompression ignition combustion for self-igniting a mixture by pistoncompression, wherein a switching engine operation between said sparkignition combustion and said compression ignition combustion accordingto engine operating conditions of said compression ignition internalcombustion engine, a vehicle driving condition of a vehicleincorporating said compression ignition internal combustion engine andan intention of a driver of said vehicle incorporating said compressionignition internal combustion engine.
 29. A compression ignition internalcombustion engine according to claim 28, wherein when an acceleratoropening is equal to or greater than a predetermined value or a vehicleacceleration is equal to or greater than a predetermined value, engineoperation is performed by said spark ignition combustion.
 30. Acompression ignition internal combustion engine according to claim 28,wherein when an accelerator opening is equal to or greater than apredetermined value or a vehicle speed is equal to or greater than apredetermined value, engine operation is performed by said sparkignition combustion.
 31. A compression ignition internal combustionengine according to claim 28, wherein when a vehicle speed is equal toor greater than a predetermined value and a brake depressing force isequal to or greater than a predetermined value, engine operation by saidcompression ignition combustion is prohibited.
 32. A compressionignition internal combustion engine according to claim 28, wherein whena cooling water temperature and a an intake air temperature are equal toor lower than a predetermined value, engine operation is performed bysaid park ignition combustion.
 33. A compression ignition internalcombustion engine according to claim 32, wherein when an exhausttemperature is equal to or higher than a predetermined value, engineoperation is switched to operation by said compression ignitioncombustion.
 34. A compression ignition internal combustion engine foroperating switching a spark ignition combustion using an ignition deviceand a compression ignition combustion for self-igniting mixture bypiston compression, wherein engine operation by said compressionignition combustion is prohibited according to engine operatingconditions of said compression ignition internal combustion engine, avehicle driving condition of a vehicle incorporating this compressionignition internal combustion engine and an intention of a driver of saidvehicle incorporating said compression ignition internal combustionengine.
 35. A compression ignition internal combustion engine accordingto claim 34, wherein when an accelerator opening is equal to or greaterthan a predetermined value or a vehicle acceleration is equal to orgreater than a predetermined value, engine operation is performed bysaid spark ignition combustion.
 36. A compression ignition internalcombustion engine according to claim 34, wherein when an acceleratoropening is equal to or greater than a predetermined value or a vehiclespeed is equal to or greater than a predetermined value, engineoperation is performed by said spark ignition combustion.
 37. Acompression ignition internal combustion engine according to claim 34,wherein when a vehicle speed is equal to or greater than a predeterminedvalue and a brake depressing force is equal to or greater than apredetermined value, engine operation by said compression ignitioncombustion is prohibited.
 38. A compression ignition internal combustionengine according to claim 34, wherein when a cooling water temperatureand an intake air temperature are equal to or lower than a predeterminedvalue, engine operation is performed by said spark ignition combustion.39. A compression ignition internal combustion engine according to claim38, wherein when an exhaust temperature is equal to or higher than apredetermined value, engine operation is switched to operation by saidcompression ignition combustion.